Investigating phenotypes of pulmonary COVID-19 recovery: A longitudinal observational prospective multicenter trial

  1. Thomas Sonnweber
  2. Piotr Tymoszuk
  3. Sabina Sahanic
  4. Anna Boehm
  5. Alex Pizzini
  6. Anna Luger
  7. Christoph Schwabl
  8. Manfred Nairz
  9. Philipp Grubwieser
  10. Katharina Kurz
  11. Sabine Koppelstätter
  12. Magdalena Aichner
  13. Bernhard Puchner
  14. Alexander Egger
  15. Gregor Hoermann
  16. Ewald Wöll
  17. Günter Weiss
  18. Gerlig Widmann
  19. Ivan Tancevski  Is a corresponding author
  20. Judith Löffler-Ragg  Is a corresponding author
  1. Department of Internal Medicine II, Medical University of Innsbruck, Austria
  2. Department of Radiology, Medical University of Innsbruck, Austria
  3. The Karl Landsteiner Institute, Austria
  4. Central Institute of Medical and Chemical Laboratory Diagnostics, University Hospital Innsbruck, Austria
  5. Munich Leukemia Laboratory, Germany
  6. Department of Internal Medicine, St. Vinzenz Hospital, Austria
10 figures, 9 tables and 2 additional files

Figures

Study inclusion flow diagram and analysis scheme.
Kinetic of recovery from COVID-19 symptoms.

Recovery from any COVID-19 symptoms was investigated by mixed-effect logistic modeling (random effect: individual; fixed effect: time). Significance was determined by the likelihood ratio test corrected for multiple testing with the Benjamini–Hochberg method, and p-values and the numbers of complete observations are indicated in the plots. (A) Frequencies of individuals with any symptoms in the study cohort stratified by acute COVID-19 severity. (B) Frequencies of participants with particular symptoms. imp.: impaired.

Figure 3 with 3 supplements
Kinetic of pulmonary recovery.

Recovery from any lung computed tomography (CT) abnormalities, moderate-to-severe lung CT abnormalities (severity score > 5), and recovery from functional lung impairment were investigated in the participants stratified by acute COVID-19 severity by mixed-effect logistic modeling (random effect: individual; fixed effect: time). Significance was determined by the likelihood ratio test corrected for multiple testing with the Benjamini–Hochberg method. Frequencies of the given abnormality at the indicated time points are presented, and p-values and the numbers of complete observations are indicated in the plots.

Figure 3—figure supplement 1
Co-occurrence of lung computed tomography (CT) abnormalities, functional lung impairment, and any persistent symptoms.

Numbers and percentages of the study participants with any persistent symptoms, functional lung impairment, or lung CT abnormalities at the consecutive follow-up visits presented in quasi-proportional Venn diagrams. The numbers of participants with CT abnormalities, lung function (LF) impairment, and persistent symptoms are indicated in the diagrams, and the numbers of complete observations are shown under the plots.

Figure 3—figure supplement 2
Co-occurrence of moderate-to-severe lung computed tomography (CT) abnormalities, functional lung impairment, and any persistent symptoms.

Numbers and percentages of the study participants with any persistent symptoms, functional lung impairment, or moderate-to-severe lung CT abnormalities (severity score > 5) at the consecutive follow-up visits presented in quasi-proportional Venn diagrams. The numbers of participants with CT abnormalities, lung function (LF) impairment, and persistent symptoms are indicated in the diagrams, and the numbers of complete observations are shown under the plots.

Figure 3—figure supplement 3
Frequency of mild and moderate-to-severe lung computed tomography (CT) abnormalities.

Prognostic value of functional lung impairment and persistent symptoms for prediction of radiological lung abnormalities. (A) Relevance of functional lung impairment and persistent COVID-19 symptoms at predicting any lung CT abnormalities and moderate-to-severe lung CT abnormalities (severity score > 5) at the consecutive follow-up visits. The concordance of the outcome variables was determined by Cohen’s κ coefficient. Statistical significance (κ ̸ = 0) was assessed by two-tailed t-test corrected for multiple testing with the Benjamini–Hochberg method. Kappa with 95% confidence intervals and p values are presented as a heat map. The number of complete observations is indicated in the plot. (B) Percentages of mild (severity score ≤ 5) and moderate-to-severe lung CT abnormalities at the consecutive follow-up visits in the study participants stratified by the severity of acute COVID-19. Statistical significance of frequency differences was determined by χ2 test for trend corrected for multiple testing with the Benjamini–Hochberg method. The number of complete observations is indicated under the plots.

Risk factors of persistent radiological lung abnormalities.

Association of 52 binary explanatory variables (Appendix 1—table 1) with the presence of any lung computed tomography (CT) abnormalities (A) or moderate-to-severe lung CT abnormalities (severity score > 5) (B) at the 180-day follow-up visit was investigated with a series of univariate logistic models (Appendix 1—table 2). Odds ratio (OR) significance was determined by Wald Z test and corrected for multiple testing with the Benjamini–Hochberg method. ORs with 95% confidence intervals for significant favorable and unfavorable factors are presented in forest plots. Model baseline (ref) and numbers of complete observations are presented in the plot axis text. Q1, Q2, Q3, Q4: first, second, third, and fourth quartile of anti-S1/S2 IgG titer; ICU: intensive care unit.

Risk factors of persistent functional lung impairment.

Association of 52 binary explanatory variables (Appendix 1—table 1) with the presence of functional lung impairment at the 180-day follow-up visit was investigated with a series of univariate logistic models (Appendix 1—table 2). Odds ratio (OR) significance was determined by Wald Z test and corrected for multiple testing with the Benjamini–Hochberg method. ORs with 95% confidence intervals for the significant favorable and unfavorable factors are presented in a forest plot. Model baseline (ref) and n numbers of complete observations are presented in the plot axis text. Q1, Q2, Q3, Q4: first, second, third, and fourth quartile of anti-S1/S2 IgG titer; CKD: chronic kidney disease.

Figure 6 with 2 supplements
Association of incomplete symptom, lung function, and radiological lung recovery with demographic and clinical parameters of acute COVID-19 and early recovery.

Clustering of 52 non-computed tomography (non-CT) and non-lung function binary explanatory variables recorded for acute COVID-19 or at the early 60-day follow-up visit (Appendix 1—table 1) was investigated by partitioning around medoids (PAM) algorithm with simple matching distance (SMD) dissimilarity measure (Figure 6—figure supplement 1, Appendix 1—table 3). The cluster assignment for the outcome variables at the 180-day follow-up visit (persistent symptoms, functional lung impairment, mild lung CT abnormalities [severity score ≤ 5] and moderate-to-severe lung CT abnormalities [severity score > 5]) was predicted by k-nearest neighbor (kNN) label propagation procedure. Numbers of complete observations and numbers of features in the clusters are indicated in (A). (A) Cluster assignment of the outcome variables (diamonds) presented in the plot of principal component (PC) scores. The first two major PCs are displayed. The explanatory variables are visualized as points. Percentages of the data set variance associated with the PC are presented in the plot axes. (B) Five nearest neighbors (lowest SMD) of the outcome variables presented in radial plots. Font size, point radius, and color code for SMD values. Q1, Q2, Q3, Q4: first, second, third, and fourth quartile of anti-S1/S2 IgG titer; GITD: gastrointestinal disease; CKD: chronic kidney disease; ICU: intensive care unit; COPD: chronic obstructive pulmonary disease.

Figure 6—figure supplement 1
Study feature clustering algorithm.

Clustering of 52 non-computed tomography (non-CT) and non-lung function binary explanatory variables recorded for acute COVID-19 or at the early 60-day follow-up visit (Appendix 1—table 1). (A, B) Comparison of ‘explained’ variances (between-cluster to total sum-of-squares ratio) (A) and cluster stability (mean classification error in 20-fold cross-validation) (B) in clustering of the data set with several algorithms with k = 3 centers/branches (algorithms: K-means; PAM: partitioning around medoids; HCl Ward.D2: hierarchical clustering with Ward.D2 method; distances: SMD: simple matching distance; Jaccard, Dice, and Cosine). (C, D) The optimal number of the feature clusters in clustering with the optimally performing PAM algorithm with SMD dissimilarity measure was determined by the bend of the total within-cluster sum-of-squares curve (C) and confirmed by good stability (low mean classification error) in 20-fold cross-validation (D).

Figure 6—figure supplement 2
Semi-supervised clustering of mild and moderate-to-severe lung computed tomography (CT) abnormalities, functional lung impairment, and persistent symptoms at the 180-day follow-up with parameters of acute COVID-19 and early convalescence.

Clusters of 52 non-CT and non-lung function binary explanatory variables recorded for acute COVID-19 or at the 60-day follow-up visit (Appendix 1—table 1) were defined by the optimally performing partitioning around medoids (PAM) algorithm and simple matching distance (SMD) dissimilarity measure (Figure 6A, Figure 6—figure supplement 1, Appendix 1—table 3). The cluster assignment for the outcome variables at the 180-day follow-up visit (persistent symptoms, functional lung impairment, mild lung CT abnormalities [severity score ≤ 5], and moderate-to-severe lung CT abnormalities [severity score > 5]) was predicted by k-nearest neighbor (kNN) label propagation procedure. SMD between the features and their cluster assignments are shown in a heat map. The numbers of features in the clusters and the total number of observations are indicated under the plot. CVD: cardiovascular disease; Q1, Q2, Q3, Q4: first, second, third, and fourth quartile of anti-S1/S2 IgG titer; GI: gastrointestinal; PD: pulmonary disease; GITD: gastrointestinal disease; ICU: intensive care unit; COPD: chronic obstructive pulmonary disease; CKD: chronic kidney disease.

Figure 7 with 2 supplements
Clustering of the study participants by non-lung function and non-computed tomography (non-CT) clinical features.

Study participants (n = 133 with the complete variable set) were clustered with respect to 52 non-CT and non-lung function binary explanatory variables recorded for acute COVID-19 or at the 60-day follow-up visit (Appendix 1—table 1) using a combined self-organizing map (SOM: simple matching distance) and hierarchical clustering (Ward.D2 method, Euclidean distance) procedure (Figure 7—figure supplement 1). The numbers of participants assigned to low-risk (LR), intermediate-risk (IR), and high-risk (HR) clusters are indicated in (A). (A) Cluster assignment of the study participants in the plot of principal component (PC) scores. The first two major PCs are displayed. Percentages of the data set variance associated with the PC are presented in the plot axes. (B) Presence of the most influential clustering features (Figure 7—figure supplement 2) in the participant clusters presented as a heat map. Cluster #1, #2, and #3 refer to the feature clusters defined in Figure 6. Q1, Q2, Q3, Q4: first, second, third, and fourth quartile of anti-S1/S2 IgG titer; GITD: gastrointestinal disease; CKD: chronic kidney disease; CVD: cardiovascular disease; GI: gastrointestinal; PD: pulmonary disease.

Figure 7—figure supplement 1
Study participant clustering algorithm.

Clustering of the study participants (n = 133 with the complete variable set) with respect to 52 non-computed tomography (non-CT) and non-lung function binary explanatory variables recorded for acute COVID-19 or at the 60-day follow-up visit (Appendix 1—table 1). The procedure involved clustering of the observations with self-organizing maps (SOM, 4 × 4 hexagonal grid, distances: SMD: simple matching distance, Jaccard, Dice, or Cosine) followed by clustering of the SOM nodes (algorithms: HCl ward.D2: hierarchical clustering with Ward.D2 method; K-means; PAM: partitioning around medoids; distance: Euclidean). Different combinations of observation dissimilarity measures and SOM node clustering algorithms were tested in the search for the optimal clustering algorithm. (A, B) Comparison of ‘explained’ variances (between-cluster to total sum-of-squares ratio) (A) and cluster stability (mean classification error in 20-fold cross-validation) (B) in clustering of the data set with different observation distance measures and SOM node clustering algorithms. (C) Training of the SOM algorithm, mean distance to the winning un as a function of lgorithm iterations is presented. Note the mean distance plateau indicative of the algorithm convergence (D–F) The optimal number of the SOM node clusters in clustering with the optimally performing SOM HCl algorithm with SMD observation dissimilarity measure. The optimal cluster number was determined by the bend of the total within-cluster sum-of-squares curve (D) and confirmed by visual inspection of the HCl dendrogram (E) and good stability (low mean classification error) in 20-fold cross-validation (F).

Figure 7—figure supplement 2
Impact of specific variables on the quality of participant clustering.

The clusters of participants clusters were defined with the optimally performing self-organizing map (SOM)/HCl algorithm with simple matching distance (SMD) observation dissimilarity measure as presented in Figure 7 and Figure 7—figure supplement 1. The impact of a particular clustering variable was determined by comparing the ‘explained’ clustering variance (between-cluster to total sum-of-squares ratio) between the initial cluster structure and the structure with random resampling of the variable. Differences in the clustering variances for the most influential clustering variables (Δ clustering variance > 0) are presented in the plot. Q1, Q3: first, third quartile of anti-S1/S2 IgG titer; CKD: chronic kidney disease; GI: gastrointestinal; CVD: cardiovascular disease; PD: pulmonary disease; GITD: gastrointestinal disease.

Figure 8 with 1 supplement
Frequency of persistent radiological lung abnormalities, functional lung impairment, and symptoms in the participant clusters.

The clusters of study participants were defined by non-lung function and non-computed tomography (non-CT) features as presented in Figure 7. Frequencies of outcome variables at the 180-day follow-up visit (mild [severity score ≤ 5], moderate-to-severe lung CT abnormalities [severity score > 5], functional lung impairment, and persistent symptoms) were compared between the low-risk (LR), intermediate-risk (IR), and high-risk (HR) participant clusters by χ2 test corrected for multiple testing with the Benjamini–Hochberg method. p-Values and numbers of participants assigned to the clusters are indicated in the plots. (A) Frequencies of the outcome features in the participant clusters. (B) Frequencies of specific symptoms in the participant clusters.

Figure 8—figure supplement 1
Risk of radiological lung abnormalities at the 180-day follow-up in the participant clusters.

The clusters of participants were defined by non-lung function and non-computed tomography (non-CT) clinical features of acute COVID-19 and early convalescence (60-day follow-up visit, Appendix 1—table 1) with the optimally performing HCl algorithm with simple matching distance (SMD) observation dissimilarity measure as presented in Figure 7 and Figure 7—figure supplement 1. (A) Distribution of mild, moderate, severe, and critical acute COVID-19 cases in the participant clusters. Significance of the distribution differences was assessed with χ2 test. The numbers of participants assigned to the clusters are indicated under the plot. (B) Association of the participant cluster assignment (LR: low-risk; IR: intermediate-risk; HR: high-risk cluster) with the risk of any lung CT abnormalities and moderate-to-severe lung CT abnormalities (severity score > 5) at the 180-day follow-up visit was investigated by logistic modeling with and without inclusion of the acute COVID-19 severity effect (severity-adjusted). Odds ratio (OR) significance was determined by Wald Z test and corrected for multiple testing with the Benjamini–Hochberg method. ORs with 95% confidence intervals are presented in forest plots. Numbers of complete observations, outcome events, participants in the clusters, and the acute COVID-19 severity subsets are indicated under the plot.

Figure 9 with 7 supplements
Prediction of persistent radiological lung abnormalities, functional lung impairment, and symptoms by machine learning algorithms.

Single machine learning classifiers (C5.0; RF: random forests; SVM-R: support vector machines with radial kernel; NNet: neural network; glmNet: elastic net) and their ensemble (Ens) were trained in the cohort data set with 52 non-computed tomography (non-CT) and non-lung function binary explanatory variables recorded for acute COVID-19 or at the 60-day follow-up visit (Appendix 1—table 1) for predicting outcome variables at the 180-day follow-up visit (any lung CT abnormalities, moderate-to-severe lung CT abnormalities [severity score > 5], functional lung impairment, and persistent symptoms) (Appendix 1—table 4). The prediction accuracy was verified by repeated 20-fold cross-validation (five repeats). Receiver-operating characteristics (ROCs) of the algorithms in the cross-validation are presented: area under the curve (AUC), sensitivity (Sens), and specificity (Spec) (Appendix 1—table 5). The numbers of complete observations and outcome events are indicated under the plots.

Figure 9—figure supplement 1
Correlation of the machine learning algorithm prediction accuracy.

Machine learning classifiers (C5.0; RF: random forests; SVM-R: support vector machines with radial kernel; NNet: neural network; glmNet: elastic net) were trained in the cohort data set with 52 non-computed tomography (non-CT) and non-lung function binary explanatory variables recorded for acute COVID-19 or at the early 60-day follow-up visit (Appendix 1—table 1) for predicting outcome variables at the 180-day follow-up visit (any lung CT abnormalities, moderate-to-severe lung CT abnormalities [severity score > 5], functional lung impairment, and persistent symptoms) (Figure 9, Appendix 1—table 4). The prediction accuracy was verified by repeated 20-fold cross-validation (five repeats). Pearson’s correlation coefficients of the classifier prediction accuracy in the cross-validation are presented as heat maps. Numbers of complete observations and outcome events are indicated under the plots.

Figure 9—figure supplement 2
Machine learning model ensembles.

Single machine learning classifiers (C5.0; RF: random forests; SVM-R: support vector machines with radial kernel; NNet: neural network; glmNet: elastic net) were trained as shown in Figure 9. The model ensembles based on the single classifiers were constructed with the glmNet procedure (Appendix 1—table 4). glmNet regression coefficients (β) are presented in the plots. Point and text color correspond to the β value. Numbers of complete observations and outcome events are indicated under the plots.

Figure 9—figure supplement 3
Prediction of persistent radiological lung abnormalities, functional lung impairment, and symptoms by machine learning algorithms in the training data sets.

Single machine learning classifiers (C5.0; RF: random forests; SVM-R: support vector machines with radial kernel; NNet: neural network; glmNet: elastic net) and their ensembles were trained as shown in Figure 9. Performance of the classifiers in the training data sets was investigated by receiver-operating characteristic (ROC) of the algorithms (AUC: area under the curve; Sens: sensitivity; Spec: specificity, Appendix 1—table 5). Numbers of complete observations and outcome events are indicated under the plots.

Figure 9—figure supplement 4
Variable importance statistics for prediction of lung computed tomography (CT) abnormalities at the 180-day follow-up by machine learning classifiers.

C5.0, random forests (RF), and elastic net (glmNet) classifiers were trained as presented in Figure 9 for prediction of any lung CT abnormalities at the 180-day follow-up visit. Variable importance measures (C5.0: % attribute/variable usage in the tree model (A); RF: difference in Gini index (B); glmNet: absolute value of the regression coefficient β (C)) for the 10 most influential explanatory variables are presented. CKD: chronic kidney disease; Q1, Q4: first, fourth quartile of anti-S1/S2 IgG titer; PD: pulmonary disease; CKD: chronic kidney disease.

Figure 9—figure supplement 5
Variable importance statistics for prediction of moderate-to-severe lung computed tomography (CT) abnormalities at the 180-day follow-up by machine learning classifiers.

C5.0, random forests (RF), and elastic net (glmNet) classifiers were trained as presented in Figure 9 for prediction of moderate-to-severe lung CT abnormalities (severity score > 5) at the 180-day follow-up visit. Variable importance measures (C5.0: % attribute/variable usage in the tree model (A); RF: difference in Gini index (B); glmNet: absolute value of the regression coefficient β (C)) for the 10 most influential explanatory variables are presented. PD: pulmonary disease; GITD: gastrointestinal disease; Q1, Q2, Q4: first, second, fourth quartile of anti-S1/S2 IgG titer.

Figure 9—figure supplement 6
Variable importance statistics for prediction of functional lung impairment at the 180-day follow-up by machine learning classifiers.

C5.0, random forests (RF), and elastic net (glmNet) classifiers were trained as presented in Figure 9 for prediction of functional lung impairment at the 180-day follow-up visit. Variable importance measures (C5.0: % attribute/variable usage in the tree model (A); RF: difference in Gini index (B); glmNet: absolute value of the regression coefficient β (C)) for the 10 most influential explanatory variables are presented. CKD: chronic kidney disease; Q1, Q2: first. second quartile of anti-S1/S2 IgG titer.

Figure 9—figure supplement 7
Variable importance statistics for prediction of persistent symptoms at the 180-day follow-up by machine learning classifiers.

C5.0, random forests (RF), and elastic net (glmNet) classifiers were trained as presented in Figure 9 for prediction of persistent symptoms at the 180-day follow-up visit. Variable importance measures (C5.0: % attribute/variable usage in the tree model (A); RF: difference in Gini index (B); glmNet: absolute value of the regression coefficient β (C)) for the 10 most influential explanatory variables are presented. CVD: cardiovascular disease; GITD: gastrointestinal disease; COPD: chronic obstructive lung disease.

Performance of the machine learning ensemble classifier in mild-to-moderate and severe-to-critical COVID-19 convalescents.

The machine learning classifier ensemble (Ens) was developed as presented in Figure 9. Its performance at predicting outcome variables at the 180-day follow-up visit (any computed tomography [CT] lung abnormalities, moderate-to-severe lung CT abnormalities [severity score > 5], functional lung impairment, and persistent symptoms) in the entire cohort, mild-to-moderate (outpatient or hospitalized without oxygen), and severe-to-critical COVID-19 convalescents (oxygen therapy or ICU) in repeated 20-fold cross-validation (five repeats) was assessed by receiver-operating characteristic (ROC) (Appendix 1—table 6). ROC curves and statistics (AUC: area under the curve; Se: sensitivity; Sp: specificity) in the cross-validation are shown. Numbers of complete observations and outcome events are indicated in the plots.

Tables

Table 1
Characteristics of the study population.
Characteristics (% cohort)
Total participants – no.145
Mean age, years57.3 (SD = 14.3)
Female sex42.4% (n = 63)
Obesity (body mass index >30 kg/m2)19.3% (n = 28)
Ex-smoker39.3% (n = 57)
Active smoker2.8% (n = 4)
Acute COVID-19 severity (% cohort)
Mild: outpatient24.8% (n = 36)
Moderate: inpatient without oxygen therapy25.5% (n = 37)
Severe: inpatient with oxygen therapy27.6% (n = 40)
Critical: intensive care unit22.1% (n = 32)
Comorbidities (% cohort)
None22.8% (n = 33)
Cardiovascular disease40% (n = 58)
Pulmonary disease18.6% (n = 27)
Metabolic disease43.4% (n = 63)
Chronic kidney disease6.9% (n = 10)
Gastrointestinal tract diseases13.8% (n = 20)
Malignancy11.7% (n = 17)
Table 2
Hospitalization and medication during acute COVID-19.
ParameterOutpatient (n = 36)Hospitalized (n = 37)Hospitalized oxygen therapy (n = 40)Hospitalized intensive care unit (n = 32)
Mean hospitalization time, days0 (SD = 0)6.9 (SD = 3.6)11.8 (SD = 6.3)34.8 (SD = 15.7)
Hospitalized >7 days0% (n = 0)43.2% (n = 16)80% (n = 32)100% (n = 32)
Anti-infectives11.1% (n = 4)45.9% (n = 17)72.5% (n = 29)87.5% (n = 28)
Antiplatelet drugs2.8% (n = 1)10.8% (n = 4)22.5% (n = 9)25% (n = 8)
Anticoagulatives2.8% (n = 1)2.7% (n = 1)5% (n = 2)15.6% (n = 5)
Corticosteroids*2.8% (n = 1)5.4% (n = 2)22.5% (n = 9)40.6% (n = 13)
Immunosuppression0% (n = 0)2.7% (n = 1)5% (n = 2)9.4% (n = 3)
  1. *

    From the week 4 post diagnosis on, at the discretion of the physician.

  2. Subsumed under ‘immunosuppression, acute COVID-19’ for data analysis.

  3. Immunosuppressive medication prior to COVID-19.

Table 3
Radiological, functional, and clinical study outcomes.
Outcome60-day follow-up100-day follow-up180-day follow-up
Any lung CT abnormalities (complete: n = 103)74.8% (n = 77)60.2% (n = 62)48.5% (n = 50)
Mild lung CT abnormalities (severity score ≤ 5) (complete: n = 103)26.2% (n = 27)36.9% (n = 38)29.1% (n = 30)
Moderate-to-severe CT abnormalities (severity score > 5) (complete: n = 103)48.5% (n = 50)23.3% (n = 24)19.4% (n = 20)
Functional lung impairment (complete: n = 116)39.7% (n = 46)37.1% (n = 43)33.6% (n = 39)
Persistent symptoms (complete: n = 145)79.3% (n = 115)67.6% (n = 98)49% (n = 71)
  1. CT = computed tomography.

Appendix 1—table 1
Study variables.

Variable: variable name in the analysis pipeline; reference time point: study visit, the variable was recorded at; label: variable label in figures and tables.

VariableReference time pointLabelVariable typeStratification cutoff
sex_male_V0Acute COVID-19Male sexExplanatory
obesity_rec_V0Acute COVID-19ObesityExplanatoryBMI > 30 kg/m2
current_smoker_V0Acute COVID-19Current smokerExplanatory
smoking_ex_V0Acute COVID-19Ex-smokerExplanatory
CVDis_rec_V0Acute COVID-19CVDExplanatory
hypertension_rec_V0Acute COVID-19HypertensionExplanatory
PDis_rec_V0Acute COVID-19PDExplanatory
COPD_rec_V0Acute COVID-19COPDExplanatory
asthma_rec_V0Acute COVID-19AsthmaExplanatory
endocrine_metabolic_rec_V0Acute COVID-19Metabolic disordersExplanatory
hypercholesterolemia_rec_V0Acute COVID-19HypercholesterolemiaExplanatory
diabetes_rec_V0Acute COVID-19DiabetesExplanatory
CKDis_rec_V0Acute COVID-19CKDExplanatory
GITDis_rec_V0Acute COVID-19GITDExplanatory
malignancy_rec_V0Acute COVID-19MalignancyExplanatory
immune_deficiency_rec_V0Acute COVID-19Immune deficiencyExplanatory
weight_change_rec_V0Acute COVID-19Weight loss, acute COVID-19Explanatory≥1 kg
dyspnoe_rec_V0Acute COVID-19Dyspnea, acute COVID-19Explanatory
cough_rec_V0Acute COVID-19Cough, acute COVID-19Explanatory
fever_rec_V0Acute COVID-19Fever, acute COVID-19Explanatory
night_sweat_rec_V0Acute COVID-19Night sweat, acute COVID-19Explanatory
pain_rec_V0Acute COVID-19Pain, acute COVID-19Explanatory
GI_sympt_rec_V0Acute COVID-19GI symptoms, acute COVID-19Explanatory
anosmia_rec_V0Acute COVID-19Anosmia, acute COVID-19Explanatory
ECOG_imp_rec_V0Acute COVID-19Impaired performance, acute COVID-19ExplanatoryECOG ≥ 1
sleep_disorder_rec_V0Acute COVID-19Sleep disorders, acute COVID-19Explanatory
treat_antiinfec_rec_V0Acute COVID-19Anti-infectives, acute COVID-19Explanatory
treat_antiplat_rec_V0Acute COVID-19Antiplatelet, acute COVID-19Explanatory
treat_anticoag_rec_V0Acute COVID-19Anticoagulatives, acute COVID-19Explanatory
treat_immunosuppr_rec_V0Acute COVID-19Immunosuppression, acute COVID-19Explanatory
anemia_rec_V160-day follow-upAnemia, 60-day visitExplanatoryMale: Hb < 14 g/dL; female: Hb <12 g/dL
ferr_elv_rec_V160-day follow-upElevated ferritin, 60-day visitExplanatoryMale: > 300 ng/mL; female: > 150 ng/mL
NTelv_rec_V160-day follow-upElevated NTproBNP, 60-day visitExplanatory>125 pg/mL
Ddimerelv_rec_V160-day follow-upElevated D-dimer, 60-day visitExplanatory>500 pg/mL FEU
CRP_elv_rec_V160-day follow-upElevated CRP, 60-day visitExplanatory>0.5 mg/dL
IL6_elv_rec_V160-day follow-upElevated IL-6, 60-day visitExplanatory>7 pg/mL
iron_deficiency_30_rec_V160-day follow-upIron deficiency, 60-day visitExplanatoryTF-saturation < 15%
age_65_V0Acute COVID-19Age over 65Explanatory>65 years
hosp_7d_V0Acute COVID-19Hospitalized > 7 days, acute COVID-19Explanatory>7 days
comorb_present_V0Acute COVID-19Any comorbidityExplanatory>0 comorbidities
comorb_3_V0Acute COVID-19>3 comorbiditiesExplanatory>3 comorbidities
overweight_V0Acute COVID-19Overweight or obesityExplanatoryBMI > 25 kg/m2
sympt_6_V0Acute COVID-19>6 symptoms, acute COVID-19Explanatory>6 symptoms
sympt_present_V160-day follow-upPersistent symptoms, 60-day visitExplanatory>0 symptoms at 180-day visit
ab_0_V160-day follow-upAnti-S1/S2 IgG Q1, 60-day visitExplanatory(0, 312] BAU/mL
ab_25_V160-day follow-upAnti-S1/S2 IgG Q2, 60-day visitExplanatory(312, 644] BAU/mL
ab_50_V160-day follow-upAnti-S1/S2 IgG Q3, 60-day visitExplanatory(644, 975] BAU/mL
ab_75_V160-day follow-upAnti-S1/S2 IgG Q4, 60-day visitExplanatory> 975 BAU/mL
pat_group_G1_V0Acute COVID-19Ambulatory, acute COVID-19Explanatory
pat_group_G2_V0Acute COVID-19Hospitalized, acute COVID-19Explanatory
pat_group_G3_V0Acute COVID-19Oxygen therapy, acute COVID-19Explanatory
pat_group_G4_V0Acute COVID-19ICU, acute COVID-19Explanatory
CT_findings_V3180-day follow-upCT abnormalities at 180-day visitOutcome
CT_sev_low_V3180-day follow-upCT severity score 1–5 at 180-day visitOutcome
CTsevabove5_V3180-day follow-upCT severity score >5 at 180-day visitOutcome
sympt_present_V3180-day follow-upSymptoms at 180-day visitOutcome
lung_function_impaired_V3180-day follow-upLung function impairment at 180-day visitOutcome
  1. CVD = cardiovascular disease; PD = pulmonary disease; COPD = chronic obstructive pulmonary disease; CKD = chronic kidney disease; GITD = gastrointestinal disease; GI = gastrointestinal; CRP = C-reactive protein; ICU = intensive care unit; CT = computed tomography; BMI = body mass index; BAU = binding antibody unit.

Appendix 1—table 2
Results of univariate risk modeling.

Outcome: outcome variable at the 180-day follow-up visit; covariate: explanatory variable; baseline: reference level of the explanatory variable; OR: odds ratios with 95% confidence intervals; pFDR: significanct p-value corrected for multiple testing with the Benjamini–Hochberg method (FDR: false discovery rate).

OutcomeCovariateBaselineComplete casesORpFDR
CT abnormalities at 180-day visitMale sex, n = 63No male sex, n = 551183.79 [1.77–8.44]p=0.01
CT abnormalities at 180-day visitObesity, n = 22No obesity, n = 961181.07 [0.415–2.72]ns (p=0.9)
CT abnormalities at 180-day visitCurrent smoker, n = 4No current smoker, n = 1141180.412 [0.02–3.33]ns (p=0.51)
CT abnormalities at 180-day visitEx-smoker, n = 48No ex-smoker, n = 701181.5 [0.716–3.16]ns (p=0.36)
CT abnormalities at 180-day visitCVD, n = 45No CVD, n = 731183.36 [1.57–7.43]p=0.012
CT abnormalities at 180-day visitHypertension, n = 34No hypertension, n = 841183.97 [1.73–9.54]p=0.01
CT abnormalities at 180-day visitPD, n = 24No PD, n = 941182.06 [0.837–5.25]ns (p=0.2)
CT abnormalities at 180-day visitCOPD, n = 6No COPD, n = 1121182.67 [0.499–19.8]ns (p=0.34)
CT abnormalities at 180-day visitAsthma, n = 9No asthma, n = 1091181.02 [0.24–4.04]ns (p=0.99)
CT abnormalities at 180-day visitMetabolic disorders, n = 50No metabolic disorders, n = 681183.14 [1.48–6.81]p=0.017
CT abnormalities at 180-day visitHypercholesterolemia, n = 22No hypercholesterolemia, n = 961182.67 [1.04–7.27]ns (p=0.093)
CT abnormalities at 180-day visitDiabetes, n = 18No diabetes, n = 1001184.07 [1.41–13.5]p=0.041
CT abnormalities at 180-day visitGITD, n = 17No GITD, n = 1011183.66 [1.25–12.2]ns (p=0.061)
CT abnormalities at 180-day visitMalignancy, n = 13No malignancy, n = 10511819.5 [3.63–362]p=0.021
CT abnormalities at 180-day visitImmune deficiency, n = 5No immune deficiency, n = 1131181.96 [0.313–15.3]ns (p=0.53)
CT abnormalities at 180-day visitWeight loss, acute COVID-19, n = 84No weight loss, acute COVID-19, n = 341184.45 [1.83–12.1]p=0.011
CT abnormalities at 180-day visitDyspnea, acute COVID-19, n = 81No dyspnea, acute COVID-19, n = 371181.45 [0.661–3.27]ns (p=0.43)
CT abnormalities at 180-day visitCough, acute COVID-19, n = 83No cough, acute COVID-19, n = 351181.07 [0.484–2.41]ns (p=0.89)
CT abnormalities at 180-day visitFever, acute COVID-19, n = 83No fever, acute COVID-19, n = 351182.56 [1.12–6.21]ns (p=0.072)
CT abnormalities at 180-day visitNight sweat, acute COVID-19, n = 74No night sweat, acute COVID-19, n = 441181.93 [0.902–4.26]ns (p=0.17)
CT abnormalities at 180-day visitPain, acute COVID-19, n = 65No pain, acute COVID-19, n = 531180.339 [0.157–0.713]p=0.021
CT abnormalities at 180-day visitGI symptoms, acute COVID-19, n = 47No GI symptoms, acute COVID-19, n = 711180.675 [0.316–1.42]ns (p=0.38)
CT abnormalities at 180-day visitAnosmia, acute COVID-19, n = 53No anosmia, acute COVID-19, n = 651181.09 [0.526–2.28]ns (p=0.85)
CT abnormalities at 180-day visitImpaired performance, acute COVID-19, n = 106No impaired performance, acute COVID-19, n = 121181.12 [0.335–3.98]ns (p=0.89)
CT abnormalities at 180-day visitSleep disorders, acute COVID-19, n = 40No sleep disorders, acute COVID-19, n = 771170.887 [0.407–1.91]ns (p=0.82)
CT abnormalities at 180-day visitAnti-infectives, acute COVID-19, n = 64No anti-infectives, acute COVID-19, n = 541183.56 [1.67–7.9]p=0.01
CT abnormalities at 180-day visitAntiplatelet, acute COVID-19, n = 12No antiplatelet, acute COVID-19, n = 1061184.4 [1.23–20.7]ns (p=0.077)
CT abnormalities at 180-day visitAnticoagulatives, acute COVID-19, n = 4No anticoagulatives, acute COVID-19, n = 1141183.98 [0.493–81.8]ns (p=0.32)
CT abnormalities at 180-day visitImmunosuppression, acute COVID-19, n = 20No immunosuppression, acute COVID-19, n = 981186.89 [2.32–25.5]p=0.01
CT abnormalities at 180-day visitAnemia, 60-day visit, n = 10No anemia, 60-day visit, n = 1081185.82 [1.38–39.8]ns (p=0.072)
CT abnormalities at 180-day visitElevated ferritin, 60-day visit, n = 20No elevated ferritin, 60-day visit, n = 981182.18 [0.825–6.01]ns (p=0.2)
CT abnormalities at 180-day visitElevated NTproBNP, 60-day visit, n = 38No elevated NTproBNP, 60-day visit, n = 801182.29 [1.05–5.1]ns (p=0.084)
CT abnormalities at 180-day visitElevated D-dimer, 60-day visit, n = 49No elevated D-dimer, 60-day visit, n = 691182.9 [1.37–6.28]p=0.023
CT abnormalities at 180-day visitElevated CRP, 60-day visit, n = 18No elevated CRP, 60-day visit, n = 1001185.71 [1.89–21.3]p=0.019
CT abnormalities at 180-day visitElevated IL-6, 60-day visit, n = 11No elevated IL-6, 60-day visit, n = 10711815.5 [2.81–289]p=0.036
CT abnormalities at 180-day visitIron deficiency, 60-day visit, n = 6No iron deficiency, 60-day visit, n = 1121180.239 [0.0123–1.55]ns (p=0.29)
CT abnormalities at 180-day visitAge over 65, n = 32No age over 65, n = 861182.81 [1.23–6.66]p=0.045
CT abnormalities at 180-day visitHospitalized >7 days, acute COVID-19, n = 59No hospitalized >7 days, acute COVID-19, n = 591184.93 [2.28–11.1]p=0.0026
CT abnormalities at 180-day visitAny comorbidity, n = 90No any comorbidity, n = 281186.86 [2.41–24.8]p=0.01
CT abnormalities at 180-day visit>3 comorbidities, n = 37No >3 comorbidities, n = 811186.05 [2.62–14.9]p=0.0026
CT abnormalities at 180-day visitOverweight or obesity, n = 72No overweight or obesity, n = 461181.61 [0.762–3.48]ns (p=0.3)
CT abnormalities at 180-day visit>6 symptoms, acute COVID-19, n = 33No >6 symptoms, acute COVID-19, n = 851180.767 [0.333–1.73]ns (p=0.59)
CT abnormalities at 180-day visitPersistent symptoms, 60-day visit, n = 93No persistent symptoms, 60-day visit, n = 251181.91 [0.769–5.08]ns (p=0.26)
CT abnormalities at 180-day visitAnti-S1/S2 IgG Q1, 60-day visit, n = 31No anti-S1/S2 IgG Q1, 60-day visit, n = 791100.0769 [0.0173–0.24]p=0.0026
CT abnormalities at 180-day visitAnti-S1/S2 IgG Q2, 60-day visit, n = 30No anti-S1/S2 IgG Q2, 60-day visit, n = 801101.12 [0.481–2.62]ns (p=0.83)
CT abnormalities at 180-day visitAnti-S1/S2 IgG Q3, 60-day visit, n = 27No anti-S1/S2 IgG Q3, 60-day visit, n = 831101.8 [0.753–4.4]ns (p=0.28)
CT abnormalities at 180-day visitAnti-S1/S2 IgG Q4, 60-day visit, n = 22No anti-S1/S2 IgG Q4, 60-day visit, n = 881105.95 [2.13–19.5]p=0.01
CT abnormalities at 180-day visitAmbulatory, acute COVID-19, n = 33No ambulatory, acute COVID-19, n = 851180.106 [0.0296–0.299]p=0.0026
CT abnormalities at 180-day visitHospitalized, acute COVID-19, n = 33No hospitalized, acute COVID-19, n = 851181.28 [0.569–2.88]ns (p=0.61)
CT abnormalities at 180-day visitOxygen therapy, acute COVID-19, n = 33No oxygen therapy, acute COVID-19, n = 851181.52 [0.676–3.43]ns (p=0.38)
CT abnormalities at 180-day visitICU, acute COVID-19, n = 19No ICU, acute COVID-19, n = 991186.28 [2.1–23.3]p=0.012
CT severity score >5 at 180-day visitMale sex, n = 63No male sex, n = 551185.1 [1.75–18.7]p=0.01
CT severity score >5 at 180-day visitObesity, n = 22No obesity, n = 961180.38 [0.0577–1.46]ns (p=0.26)
CT severity score >5 at 180-day visitCurrent smoker, n = 4No current smoker, n = 1141181.48 [0.0711–12.2]ns (p=0.77)
CT severity score >5 at 180-day visitEx-smoker, n = 48No ex-smoker, n = 701181.59 [0.623–4.09]ns (p=0.37)
CT severity score >5 at 180-day visitCVD, n = 45No CVD, n = 731184.71 [1.8–13.5]p=0.0042
CT severity score >5 at 180-day visitHypertension, n = 34No hypertension, n = 841183.17 [1.21–8.38]p=0.029
CT severity score >5 at 180-day visitPD, n = 24No PD, n = 941182.17 [0.735–6.02]ns (p=0.18)
CT severity score >5 at 180-day visitCOPD, n = 6No COPD, n = 1121182.3 [0.304–12.7]ns (p=0.39)
CT severity score >5 at 180-day visitAsthma, n = 9No asthma, n = 1091182.37 [0.468–9.85]ns (p=0.29)
CT severity score >5 at 180-day visitMetabolic disorders, n = 50No metabolic disorders, n = 681182.92 [1.14–7.95]p=0.045
CT severity score >5 at 180-day visitHypercholesterolemia, n = 22No hypercholesterolemia, n = 961182.52 [0.845–7.12]ns (p=0.12)
CT severity score >5 at 180-day visitDiabetes, n = 18No diabetes, n = 1001182.63 [0.816–7.87]ns (p=0.12)
CT severity score >5 at 180-day visitCKD, n = 6No CKD, n = 1121184.89 [0.851–28.3]ns (p=0.091)
CT severity score >5 at 180-day visitGITD, n = 17No GITD, n = 1011182.9 [0.892–8.83]ns (p=0.092)
CT severity score >5 at 180-day visitMalignancy, n = 13No malignancy, n = 1051180.333 [0.0178–1.84]ns (p=0.35)
CT severity score >5 at 180-day visitImmune deficiency, n = 5No immune deficiency, n = 1131187.42 [1.16–59.3]ns (p=0.052)
CT severity score >5 at 180-day visitWeight loss, acute COVID-19, n = 84No weight loss, acute COVID-19, n = 341183.02 [0.939–13.5]ns (p=0.13)
CT severity score >5 at 180-day visitDyspnea, acute COVID-19, n = 81No dyspnea, acute COVID-19, n = 371181.7 [0.609–5.54]ns (p=0.38)
CT severity score >5 at 180-day visitCough, acute COVID-19, n = 83No cough, acute COVID-19, n = 351180.537 [0.206–1.44]ns (p=0.25)
CT severity score >5 at 180-day visitFever, acute COVID-19, n = 83No fever, acute COVID-19, n = 351182.15 [0.727–7.9]ns (p=0.24)
CT severity score >5 at 180-day visitNight sweat, acute COVID-19, n = 74No night sweat, acute COVID-19, n = 441182.33 [0.84–7.55]ns (p=0.17)
CT severity score >5 at 180-day visitPain, acute COVID-19, n = 65No pain, acute COVID-19, n = 531180.495 [0.187–1.26]ns (p=0.18)
CT severity score >5 at 180-day visitGI symptoms, acute COVID-19, n = 47No GI symptoms, acute COVID-19, n = 711180.503 [0.168–1.34]ns (p=0.23)
CT severity score >5 at 180-day visitAnosmia, acute COVID-19, n = 53No anosmia, acute COVID-19, n = 651181.61 [0.634–4.16]ns (p=0.36)
CT severity score >5 at 180-day visitImpaired performance, acute COVID-19, n = 106No impaired performance, acute COVID-19, n = 121182.72 [0.486–51]ns (p=0.39)
CT severity score >5 at 180-day visitSleep disorders, acute COVID-19, n = 40No sleep disorders, acute COVID-19, n = 771171.13 [0.412–2.91]ns (p=0.84)
CT severity score >5 at 180-day visitAnti-infectives, acute COVID-19, n = 64No anti-infectives, acute COVID-19, n = 541184.89 [1.68–17.9]p=0.012
CT severity score >5 at 180-day visitAntiplatelet, acute COVID-19, n = 12No antiplatelet, acute COVID-19, n = 1061183.74 [1.01–13.2]ns (p=0.06)
CT severity score >5 at 180-day visitAnticoagulatives, acute COVID-19, n = 4No anticoagulatives, acute COVID-19, n = 1141184.7 [0.538–41.1]ns (p=0.17)
CT severity score >5 at 180-day visitImmunosuppression, acute COVID-19, n = 20No immunosuppression, acute COVID-19, n = 981185.35 [1.85–15.6]p=0.0036
CT severity score >5 at 180-day visitAnemia, 60-day visit, n = 10No anemia, 60-day visit, n = 1081188.62 [2.23–37.1]p=0.0039
CT severity score >5 at 180-day visitElevated ferritin, 60-day visit, n = 20No elevated ferritin, 60-day visit, n = 981182.2 [0.693–6.42]ns (p=0.2)
CT severity score >5 at 180-day visitElevated NTproBNP, 60-day visit, n = 38No elevated NTproBNP, 60-day visit, n = 801183.23 [1.25–8.55]p=0.026
CT severity score >5 at 180-day visitElevated D-dimer, 60-day visit, n = 49No elevated D-dimer, 60-day visit, n = 691182.41 [0.945–6.38]ns (p=0.096)
CT severity score >5 at 180-day visitElevated CRP, 60-day visit, n = 18No elevated CRP, 60-day visit, n = 1001184.91 [1.63–14.7]p=0.0075
CT severity score >5 at 180-day visitElevated IL-6, 60-day visit, n = 11No elevated IL-6, 60-day visit, n = 10711832.5 [7.43–230]p=7.5e-05
CT severity score >5 at 180-day visitIron deficiency, 60-day visit, n = 6No iron deficiency, 60-day visit, n = 1121180.867 [0.044–5.75]ns (p=0.92)
CT severity score >5 at 180-day visitAge over 65, n = 32No age over 65, n = 861182.8 [1.05–7.4]ns (p=0.055)
CT severity score >5 at 180-day visitHospitalized >7 days, acute COVID-19, n = 59No hospitalized >7 days, acute COVID-19, n = 591184.37 [1.58–14.2]p=0.012
CT severity score >5 at 180-day visitAny comorbidity, n = 90No any comorbidity, n = 281188.22 [1.59–151]ns (p=0.065)
CT severity score >5 at 180-day visit>3 comorbidities, n = 37No >3 comorbidities, n = 811185.55 [2.11–15.5]p=0.0013
CT severity score >5 at 180-day visitOverweight or obesity, n = 72No overweight or obesity, n = 461180.72 [0.282–1.87]ns (p=0.53)
CT severity score >5 at 180-day visit>6 symptoms, acute COVID-19, n = 33No >6 symptoms, acute COVID-19, n = 851181.26 [0.438–3.35]ns (p=0.69)
CT severity score >5 at 180-day visitPersistent symptoms, 60-day visit, n = 93No persistent symptoms, 60-day visit, n = 251183.15 [0.831–20.7]ns (p=0.18)
CT severity score >5 at 180-day visitAnti-S1/S2 IgG Q2, 60-day visit, n = 30No anti-S1/S2 IgG Q2, 60-day visit, n = 801101.87 [0.666–5.07]ns (p=0.26)
CT severity score >5 at 180-day visitAnti-S1/S2 IgG Q3, 60-day visit, n = 27No anti-S1/S2 IgG Q3, 60-day visit, n = 831100.675 [0.18–2.05]ns (p=0.55)
CT severity score >5 at 180-day visitAnti-S1/S2 IgG Q4, 60-day visit, n = 22No anti-S1/S2 IgG Q4, 60-day visit, n = 881104.38 [1.53–12.6]p=0.01
CT severity score >5 at 180-day visitAmbulatory, acute COVID-19, n = 33No ambulatory, acute COVID-19, n = 851180.0952 [0.0052–0.488]p=0.039
CT severity score >5 at 180-day visitHospitalized, acute COVID-19, n = 33No hospitalized, acute COVID-19, n = 851180.714 [0.218–2.01]ns (p=0.58)
CT severity score >5 at 180-day visitOxygen therapy, acute COVID-19, n = 33No oxygen therapy, acute COVID-19, n = 851180.958 [0.316–2.61]ns (p=0.95)
CT severity score >5 at 180-day visitICU, acute COVID-19, n = 19No ICU, acute COVID-19, n = 991188.06 [2.75–24.5]p=0.00035
Symptoms at 180-day visitMale sex, n = 82No male sex, n = 631450.701 [0.361–1.35]ns (p=0.97)
Symptoms at 180-day visitObesity, n = 28No obesity, n = 1171450.42 [0.169–0.982]ns (p=0.84)
Symptoms at 180-day visitCurrent smoker, n = 4No current smoker, n = 1411453.22 [0.401–66]ns (p=0.97)
Symptoms at 180-day visitEx-smoker, n = 57No ex-smoker, n = 881451.27 [0.654–2.49]ns (p=0.97)
Symptoms at 180-day visitCVD, n = 58No CVD, n = 871450.851 [0.436–1.66]ns (p=0.97)
Symptoms at 180-day visitHypertension, n = 44No hypertension, n = 1011450.931 [0.456–1.89]ns (p=0.97)
Symptoms at 180-day visitPD, n = 27No PD, n = 1181451.38 [0.598–3.26]ns (p=0.97)
Symptoms at 180-day visitCOPD, n = 8No COPD, n = 1371451.04 [0.238–4.58]ns (p=0.97)
Symptoms at 180-day visitAsthma, n = 10No asthma, n = 1351451.05 [0.279–3.92]ns (p=0.97)
Symptoms at 180-day visitMetabolic disorders, n = 63No metabolic disorders, n = 821451.02 [0.527–1.96]ns (p=0.97)
Symptoms at 180-day visitHypercholesterolemia, n = 27No hypercholesterolemia, n = 1181450.55 [0.226–1.28]ns (p=0.97)
Symptoms at 180-day visitDiabetes, n = 24No diabetes, n = 1211451.05 [0.434–2.54]ns (p=0.97)
Symptoms at 180-day visitCKD, n = 10No CKD, n = 1351451.62 [0.442–6.56]ns (p=0.97)
Symptoms at 180-day visitGITD, n = 20No GITD, n = 1251451.68 [0.649–4.55]ns (p=0.97)
Symptoms at 180-day visitMalignancy, n = 17No malignancy, n = 1281450.7 [0.241–1.94]ns (p=0.97)
Symptoms at 180-day visitImmune deficiency, n = 9No immune deficiency, n = 1361450.824 [0.197–3.24]ns (p=0.97)
Symptoms at 180-day visitWeight loss, acute COVID-19, n = 106No weight loss, acute COVID-19, n = 391451.34 [0.644–2.84]ns (p=0.97)
Symptoms at 180-day visitDyspnea, acute COVID-19, n = 98No dyspnea, acute COVID-19, n = 471452.84 [1.39–6.04]ns (p=0.2)
Symptoms at 180-day visitCough, acute COVID-19, n = 102No cough, acute COVID-19, n = 431451.97 [0.96–4.17]ns (p=0.88)
Symptoms at 180-day visitFever, acute COVID-19, n = 106No fever, acute COVID-19, n = 391451.17 [0.559–2.45]ns (p=0.97)
Symptoms at 180-day visitNight sweat, acute COVID-19, n = 92No night sweat, acute COVID-19, n = 531451.42 [0.723–2.83]ns (p=0.97)
Symptoms at 180-day visitPain, acute COVID-19, n = 78No pain, acute COVID-19, n = 671451.92 [0.993–3.75]ns (p=0.84)
Symptoms at 180-day visitGI symptoms, acute COVID-19, n = 59No GI symptoms, acute COVID-19, n = 861451.27 [0.656–2.48]ns (p=0.97)
Symptoms at 180-day visitAnosmia, acute COVID-19, n = 62No anosmia, acute COVID-19, n = 831451.69 [0.874–3.31]ns (p=0.96)
Symptoms at 180-day visitImpaired performance, acute COVID-19, n = 132No impaired performance, acute COVID-19, n = 131451.13 [0.358–3.69]ns (p=0.97)
Symptoms at 180-day visitSleep disorders, acute COVID-19, n = 56No sleep disorders, acute COVID-19, n = 881441.38 [0.708–2.73]ns (p=0.97)
Symptoms at 180-day visitAnti-infectives, acute COVID-19, n = 78No anti-infectives, acute COVID-19, n = 671450.701 [0.362–1.35]ns (p=0.97)
Symptoms at 180-day visitAntiplatelet, acute COVID-19, n = 22No antiplatelet, acute COVID-19, n = 1231451.05 [0.42–2.63]ns (p=0.97)
Symptoms at 180-day visitAnticoagulatives, acute COVID-19, n = 9No anticoagulatives, acute COVID-19, n = 1361452.18 [0.553–10.7]ns (p=0.97)
Symptoms at 180-day visitImmunosuppression, acute COVID-19, n = 27No immunosuppression, acute COVID-19, n = 1181451.38 [0.598–3.26]ns (p=0.97)
Symptoms at 180-day visitAnemia, 60-day visit, n = 16No anemia, 60-day visit, n = 1291450.591 [0.191–1.69]ns (p=0.97)
Symptoms at 180-day visitElevated ferritin, 60-day visit, n = 26No elevated ferritin, 60-day visit, n = 1181441.29 [0.551–3.07]ns (p=0.97)
Symptoms at 180-day visitElevated NTproBNP, 60-day visit, n = 52No elevated NTproBNP, 60-day visit, n = 931451.96 [0.987–3.94]ns (p=0.84)
Symptoms at 180-day visitElevated D-dimer, 60-day visit, n = 60No elevated D-dimer, 60-day visit, n = 851451.7 [0.874–3.33]ns (p=0.96)
Symptoms at 180-day visitElevated CRP, 60-day visit, n = 23No elevated CRP, 60-day visit, n = 1221451.16 [0.475–2.88]ns (p=0.97)
Symptoms at 180-day visitElevated IL-6, 60-day visit, n = 17No elevated IL-6, 60-day visit, n = 1281450.529 [0.173–1.48]ns (p=0.97)
Symptoms at 180-day visitIron deficiency, 60-day visit, n = 6No iron deficiency, 60-day visit, n = 1381442.18 [0.412–16.1]ns (p=0.97)
Symptoms at 180-day visitAge over 65, n = 43No age over 65, n = 1021451.69 [0.827–3.51]ns (p=0.97)
Symptoms at 180-day visitHospitalized >7 days, acute COVID-19, n = 80No hospitalized >7 days, acute COVID-19, n = 651451.1 [0.569–2.12]ns (p=0.97)
Symptoms at 180-day visitAny comorbidity, n = 112No any comorbidity, n = 331451.03 [0.47–2.24]ns (p=0.97)
Symptoms at 180-day visit>3 comorbidities, n = 47No >3 comorbidities, n = 981451.46 [0.727–2.95]ns (p=0.97)
Symptoms at 180-day visitOverweight or obesity, n = 86No overweight or obesity, n = 591450.7 [0.358–1.36]ns (p=0.97)
Symptoms at 180-day visit>6 symptoms, acute COVID-19, n = 42No >6 symptoms, acute COVID-19, n = 1031451.82 [0.885–3.82]ns (p=0.96)
Symptoms at 180-day visitPersistent symptoms, 60-day visit, n = 115No persistent symptoms, 60-day visit, n = 301454.12 [1.71–11.1]ns (p=0.2)
Symptoms at 180-day visitAnti-S1/S2 IgG Q1, 60-day visit, n = 34No anti-S1/S2 IgG Q1, 60-day visit, n = 1001341.04 [0.476–2.28]ns (p=0.97)
Symptoms at 180-day visitAnti-S1/S2 IgG Q2, 60-day visit, n = 33No anti-S1/S2 IgG Q2, 60-day visit, n = 1011341.13 [0.512–2.49]ns (p=0.97)
Symptoms at 180-day visitAnti-S1/S2 IgG Q3, 60-day visit, n = 34No anti-S1/S2 IgG Q3, 60-day visit, n = 1001340.646 [0.289–1.41]ns (p=0.97)
Symptoms at 180-day visitAnti-S1/S2 IgG Q4, 60-day visit, n = 33No anti-S1/S2 IgG Q4, 60-day visit, n = 1011341.32 [0.603–2.95]ns (p=0.97)
Symptoms at 180-day visitAmbulatory, acute COVID-19, n = 36No ambulatory, acute COVID-19, n = 1091450.911 [0.426–1.94]ns (p=0.97)
Symptoms at 180-day visitHospitalized, acute COVID-19, n = 37No hospitalized, acute COVID-19, n = 1081450.983 [0.463–2.08]ns (p=0.97)
Symptoms at 180-day visitOxygen therapy, acute COVID-19, n = 40No oxygen therapy, acute COVID-19, n = 1051450.922 [0.442–1.91]ns (p=0.97)
Symptoms at 180-day visitICU, acute COVID-19, n = 32No ICU, acute COVID-19, n = 1131451.24 [0.564–2.74]ns (p=0.97)
Lung function impairment at 180-day visitMale sex, n = 71No male sex, n = 511222.12 [0.964–4.85]ns (p=0.1)
Lung function impairment at 180-day visitObesity, n = 22No obesity, n = 1001221.94 [0.746–5]ns (p=0.22)
Lung function impairment at 180-day visitCurrent smoker, n = 3No current smoker, n = 1191224.26 [0.397–93.4]ns (p=0.3)
Lung function impairment at 180-day visitEx-smoker, n = 45No ex-smoker, n = 771221.95 [0.897–4.26]ns (p=0.13)
Lung function impairment at 180-day visitCVD, n = 49No CVD, n = 731221.57 [0.727–3.39]ns (p=0.31)
Lung function impairment at 180-day visitHypertension, n = 35No hypertension, n = 871221.56 [0.683–3.54]ns (p=0.34)
Lung function impairment at 180-day visitPD, n = 23No PD, n = 991222.21 [0.869–5.62]ns (p=0.13)
Lung function impairment at 180-day visitCOPD, n = 7No COPD, n = 1151222.93 [0.615–15.5]ns (p=0.23)
Lung function impairment at 180-day visitAsthma, n = 9No asthma, n = 1131221.03 [0.208–4.12]ns (p=0.97)
Lung function impairment at 180-day visitMetabolic disorders, n = 53No metabolic disorders, n = 691221.73 [0.807–3.73]ns (p=0.22)
Lung function impairment at 180-day visitHypercholesterolemia, n = 24No hypercholesterolemia, n = 981221.03 [0.383–2.61]ns (p=0.96)
Lung function impairment at 180-day visitDiabetes, n = 21No diabetes, n = 1011222.15 [0.816–5.64]ns (p=0.16)
Lung function impairment at 180-day visitCKD, n = 8No CKD, n = 11412217.2 [2.9–328]p=0.02
Lung function impairment at 180-day visitGITD, n = 16No GITD, n = 1061223.11 [1.07–9.42]ns (p=0.061)
Lung function impairment at 180-day visitMalignancy, n = 14No malignancy, n = 1081224.47 [1.43–15.6]p=0.025
Lung function impairment at 180-day visitImmune deficiency, n = 6No immune deficiency, n = 1161222.14 [0.38–12]ns (p=0.43)
Lung function impairment at 180-day visitWeight loss, acute COVID-19, n = 91No weight loss, acute COVID-19, n = 311221.56 [0.645–4.08]ns (p=0.41)
Lung function impairment at 180-day visitDyspnea, acute COVID-19, n = 82No dyspnea, acute COVID-19, n = 401223.17 [1.31–8.58]p=0.029
Lung function impairment at 180-day visitCough, acute COVID-19, n = 88No cough, acute COVID-19, n = 341220.856 [0.375–2.01]ns (p=0.76)
Lung function impairment at 180-day visitFever, acute COVID-19, n = 92No fever, acute COVID-19, n = 301221.19 [0.496–3.01]ns (p=0.76)
Lung function impairment at 180-day visitNight sweat, acute COVID-19, n = 79No night sweat, acute COVID-19, n = 431220.39 [0.176–0.852]p=0.033
Lung function impairment at 180-day visitPain, acute COVID-19, n = 65No pain, acute COVID-19, n = 571220.609 [0.282–1.3]ns (p=0.26)
Lung function impairment at 180-day visitGI symptoms, acute COVID-19, n = 46No GI symptoms, acute COVID-19, n = 761220.715 [0.316–1.57]ns (p=0.47)
Lung function impairment at 180-day visitAnosmia, acute COVID-19, n = 51No anosmia, acute COVID-19, n = 711220.895 [0.41–1.92]ns (p=0.82)
Lung function impairment at 180-day visitImpaired performance, acute COVID-19, n = 111No impaired performance, acute COVID-19, n = 111220.84 [0.238–3.38]ns (p=0.82)
Lung function impairment at 180-day visitSleep disorders, acute COVID-19, n = 46No sleep disorders, acute COVID-19, n = 751210.7 [0.309–1.54]ns (p=0.44)
Lung function impairment at 180-day visitAnti-infectives, acute COVID-19, n = 63No anti-infectives, acute COVID-19, n = 591222.65 [1.22–6]p=0.03
Lung function impairment at 180-day visitAntiplatelet, acute COVID-19, n = 17No antiplatelet, acute COVID-19, n = 1051224.8 [1.67–15.1]p=0.011
Lung function impairment at 180-day visitAnticoagulatives, acute COVID-19, n = 7No anticoagulatives, acute COVID-19, n = 1151222.93 [0.615–15.5]ns (p=0.23)
Lung function impairment at 180-day visitImmunosuppression, acute COVID-19, n = 22No immunosuppression, acute COVID-19, n = 1001222.45 [0.95–6.34]ns (p=0.096)
Lung function impairment at 180-day visitAnemia, 60-day visit, n = 11No anemia, 60-day visit, n = 1111224.14 [1.17–16.7]ns (p=0.053)
Lung function impairment at 180-day visitElevated ferritin, 60-day visit, n = 21No elevated ferritin, 60-day visit, n = 1001211.37 [0.498–3.6]ns (p=0.58)
Lung function impairment at 180-day visitElevated NTproBNP, 60-day visit, n = 44No elevated NTproBNP, 60-day visit, n = 781222.42 [1.11–5.33]p=0.046
Lung function impairment at 180-day visitElevated D-dimer, 60-day visit, n = 50No elevated D-dimer, 60-day visit, n = 721223.23 [1.49–7.2]p=0.0089
Lung function impairment at 180-day visitElevated CRP, 60-day visit, n = 17No elevated CRP, 60-day visit, n = 1051226.6 [2.24–22.3]p=0.0029
Lung function impairment at 180-day visitElevated IL-6, 60-day visit, n = 9No elevated IL-6, 60-day visit, n = 11312220.2 [3.52–383]p=0.013
Lung function impairment at 180-day visitIron deficiency, 60-day visit, n = 6No iron deficiency, 60-day visit, n = 1151211.05 [0.142–5.65]ns (p=0.96)
Lung function impairment at 180-day visitAge over 65, n = 33No age over 65, n = 891222.55 [1.11–5.88]p=0.046
Lung function impairment at 180-day visitHospitalized >7 days, acute COVID-19, n = 66No hospitalized >7 days, acute COVID-19, n = 561223.83 [1.7–9.21]p=0.0045
Lung function impairment at 180-day visitAny comorbidity, n = 93No any comorbidity, n = 291223.95 [1.39–14.2]p=0.032
Lung function impairment at 180-day visit>3 comorbidities, n = 41No >3 comorbidities, n = 811222.47 [1.12–5.48]p=0.044
Lung function impairment at 180-day visitOverweight or obesity, n = 72No overweight or obesity, n = 501221.24 [0.575–2.73]ns (p=0.64)
Lung function impairment at 180-day visit>6 symptoms, acute COVID-19, n = 34No >6 symptoms, acute COVID-19, n = 881220.538 [0.207–1.29]ns (p=0.23)
Lung function impairment at 180-day visitPersistent symptoms, 60-day visit, n = 96No persistent symptoms, 60-day visit, n = 261221.83 [0.702–5.39]ns (p=0.3)
Lung function impairment at 180-day visitAnti-S1/S2 IgG Q1, 60-day visit, n = 28No anti-S1/S2 IgG Q1, 60-day visit, n = 841120.245 [0.0675–0.704]p=0.03
Lung function impairment at 180-day visitAnti-S1/S2 IgG Q2, 60-day visit, n = 27No anti-S1/S2 IgG Q2, 60-day visit, n = 851122.23 [0.913–5.45]ns (p=0.12)
Lung function impairment at 180-day visitAnti-S1/S2 IgG Q3, 60-day visit, n = 28No anti-S1/S2 IgG Q3, 60-day visit, n = 841120.72 [0.27–1.78]ns (p=0.55)
Lung function impairment at 180-day visitAnti-S1/S2 IgG Q4, 60-day visit, n = 29No anti-S1/S2 IgG Q4, 60-day visit, n = 831121.88 [0.784–4.51]ns (p=0.21)
Lung function impairment at 180-day visitAmbulatory, acute COVID-19, n = 32No ambulatory, acute COVID-19, n = 901220.214 [0.0597–0.603]p=0.017
Lung function impairment at 180-day visitHospitalized, acute COVID-19, n = 32No hospitalized, acute COVID-19, n = 901221.1 [0.458–2.56]ns (p=0.85)
Lung function impairment at 180-day visitOxygen therapy, acute COVID-19, n = 32No oxygen therapy, acute COVID-19, n = 901221.33 [0.561–3.07]ns (p=0.57)
Lung function impairment at 180-day visitICU, acute COVID-19, n = 26No ICU, acute COVID-19, n = 961222.56 [1.05–6.27]ns (p=0.061)
  1. CVD = cardiovascular disease; PD = pulmonary disease; COPD = chronic obstructive pulmonary disease; CKD = chronic kidney disease; GITD = gastrointestinal disease; GI = gastrointestinal; CRP = C-reactive protein; ICU = intensive care unit; CT = computed tomography.

Appendix 1—table 3
Feature cluster assignment scheme.
Cluster #Variable
1Male sex, CVD, hypertension, metabolic disorders, anti-infectives, acute COVID-19, elevated NTproBNP, 60-day visit, elevated D-dimer, 60-day visit, hospitalized >7 days, acute COVID-19, >3 comorbidities, overweight
2Obesity, current smoker, ex-smoker, PD, COPD, asthma, hypercholesterolemia, diabetes, CKD, GITD, malignancy, immune deficiency, GI symptoms, acute COVID-19, anosmia, acute COVID-19, sleep disorders, acute COVID-19, antiplatelet, acute COVID-19, anticoagulatives, acute COVID-19, immunosuppression, acute COVID-19, anemia, 60-day visit, elevated ferritin, 60-day visit, elevated CRP, 60-day visit, elevated IL-6, 60-day visit, iron deficiency, 60-day visit, age over 65, > 6 symptoms, acute COVID-19, anti-S1/S2 IgG Q1, 60-day visit, anti-S1/S2 IgG Q2, 60-day visit, anti-S1/S2 IgG Q3, 60-day visit, anti-S1/S2 IgG Q4, 60-day visit, ambulatory, acute COVID-19, hospitalized, acute COVID-19, oxygen therapy, acute COVID-19, ICU, acute COVID-19, CT severity score 1–5 at 180-day visit, CT severity score >5 at 180-day visit, lung function impairment at 180-day visit
3Weight loss, acute COVID-19, dyspnea, acute COVID-19, cough, acute COVID-19, fever, acute COVID-19, night sweat, acute COVID-19, pain, acute COVID-19, impaired performance, acute COVID-19, any comorbidity, persistent symptoms, 60-day visit, symptoms at 180-day visit
  1. CVD = cardiovascular disease; PD = pulmonary disease; COPD = chronic obstructive pulmonary disease; CKD = chronic kidney disease; GITD = gastrointestinal disease; GI = gastrointestinal; CRP = C-reactive protein; ICU = intensive care unit; CT = computed tomography.

Appendix 1—table 4
Development of machine learning models.

Outcome: outcome variable at the 180-day follow-up visit

OutcomeClassifier typeCaret methodDescriptionPackageOptimal arguments
CT abnormalities at 180-day visitmodelC5.0C5.0C50trials = 10, model = tree, winnow = FALSE
rfRandom ForestrandomForestmtry = 27
svmRadialSupport Vector Machines with Radial Basis Function Kernelkernlabsigma = 0.0105, C = 0.5
nnetNeural Networknnetsize = 1, decay = 0
glmnetElastic-Net Regularized Generalized Linear Modelsglmnetalpha = 0.1, lambda = 0.000431
ensembleglmnetElastic-Net Regularized Generalized Linear Modelsglmnetalpha = 1, lambda = 0.0523
CT severity score >5 at 180-day visitmodelC5.0C5.0C50trials = 1, model = rules, winnow = TRUE
rfRandom ForestrandomForestmtry = 52
svmRadialSupport Vector Machines with Radial Basis Function Kernelkernlabsigma = 0.00979, C = 0.5
nnetNeural Networknnetsize = 1, decay = 0.1
glmnetElastic-Net Regularized Generalized Linear Modelsglmnetalpha = 0.1, lambda = 0.0419
ensembleglmnetElastic-Net Regularized Generalized Linear Modelsglmnetalpha = 0.1, lambda = 0.00379
Symptoms at 180-day visitmodelC5.0C5.0C50trials = 1, model = tree, winnow = FALSE
rfRandom ForestrandomForestmtry = 27
svmRadialSupport Vector Machines with Radial Basis Function Kernelkernlabsigma = 0.0109, C = 1
nnetNeural Networknnetsize = 3, decay = 0.1
glmnetElastic-Net Regularized Generalized Linear Modelsglmnetalpha = 0.1, lambda = 0.000247
ensembleglmnetElastic-Net Regularized Generalized Linear Modelsglmnetalpha = 0.1, lambda = 0.0167
Lung function impairment at 180-day visitmodelC5.0C5.0C50trials = 1, model = rules, winnow = FALSE
rfRandom ForestrandomForestmtry = 52
svmRadialSupport Vector Machines with Radial Basis Function Kernelkernlabsigma = 0.0108, C = 0.5
nnetNeural Networknnetsize = 1, decay = 0.1
glmnetElastic-Net Regularized Generalized Linear Modelsglmnetalpha = 0.55, lambda = 0.0341
ensembleglmnetElastic-Net Regularized Generalized Linear Modelsglmnetalpha = 0.55, lambda = 0.0387
Appendix 1—table 5
Performance of machine learning classifiers.

Outcome: outcome variable at the 180-day follow-up visit; Method: Caret method, Accuracy: model accuracy with 95% confidence intervals, Kappa: model kappa statistic with 95% confidence intervals, AUC: area under the curve.

OutcomeTotal NEvents NMethodData setAccuracyKappaAUCSensitivitySpecificity
CT abnormalities at 180-day visit10949C5.0CV0.72 [0.36–1]0.43 [-0.35–1]0.780.690.74
CT abnormalities at 180-day visit10949C5.0Training11111
CT abnormalities at 180-day visit10949ensembleCV0.78 [0.63–0.93]0.55 [0.26–0.85]0.810.750.8
CT abnormalities at 180-day visit10949ensembleTraining0.930.850.980.860.98
CT abnormalities at 180-day visit10949glmnetCV0.71 [0.3–1]0.42 [-0.52–1]0.790.710.72
CT abnormalities at 180-day visit10949glmnetTraining11111
CT abnormalities at 180-day visit10949nnetcCV0.67 [0.26–1]0.35 [-0.38–1]0.690.710.64
CT abnormalities at 180-day visit10949nnetTraining0.760.540.7810.57
CT abnormalities at 180-day visit10949rfCV0.73 [0.4–1]0.45 [-0.33–1]0.780.720.74
CT abnormalities at 180-day visit10949rfTraining11111
CT abnormalities at 180-day visit10949svmRadialCV0.75 [0.4–1]0.51 [-0.25–1]0.80.780.73
CT abnormalities at 180-day visit10949svmRadialTraining0.850.70.930.840.87
CT severity score >5 at 180-day visit10921C5.0CV0.86 [0.67–1]0.37 [-0.2–1]0.70.390.98
CT severity score >5 at 180-day visit10921C5.0Training0.870.50.70.430.98
CT severity score >5 at 180-day visit10921ensembleCV0.88 [0.81–0.96]0.51 [0.044–0.89]0.750.450.98
CT severity score >5 at 180-day visit10921ensembleTraining0.890.570.650.480.99
CT severity score >5 at 180-day visit10921glmnetCV0.84 [0.6–1]0.34 [-0.25–1]0.760.410.94
CT severity score >5 at 180-day visit10921glmnetTraining0.940.80.970.711
CT severity score >5 at 180-day visit10921nnetCV0.79 [0.5–1]0.31 [-0.29–1]0.720.470.87
CT severity score >5 at 180-day visit10921nnetTraining0.990.9710.951
CT severity score >5 at 180-day visit10921rfCV0.84 [0.6–1]0.34 [-0.25–1]0.730.40.95
CT severity score >5 at 180-day visit10921rfTraining11111
CT severity score >5 at 180-day visit10921svmRadialCV0.87 [0.63–1]0.43 [-0.23–1]0.750.480.97
CT severity score >5 at 180-day visit10921svmRadialTraining0.920.680.990.571
Lung function impairment at 180-day visit11138C5.0CV0.73 [0.33–1]0.39 [-0.5–1]0.70.540.84
Lung function impairment at 180-day visit11138C5.0Training0.860.70.850.790.9
Lung function impairment at 180-day visit11138ensembleCV0.75 [0.61–0.86]0.39 [0.052–0.67]0.720.480.89
Lung function impairment at 180-day visit11138ensembleTraining0.890.750.980.790.95
Lung function impairment at 180-day visit11138glmnetCV0.74 [0.4–1]0.37 [-0.36–1]0.660.510.86
Lung function impairment at 180-day visit11138glmnetTraining0.830.590.890.610.95
Lung function impairment at 180-day visit11138nnetCV0.65 [0.2–1]0.2 [-0.5–1]0.590.440.76
Lung function impairment at 180-day visit11138nnetTraining0.930.830.820.791
Lung function impairment at 180-day visit11138rfCV0.73 [0.4–1]0.35 [-0.33–1]0.720.490.85
Lung function impairment at 180-day visit11138rfTraining11111
Lung function impairment at 180-day visit11138svmRadialCV0.72 [0.36–1]0.35 [-0.44–1]0.690.50.84
Lung function impairment at 180-day visit11138svmRadialTraining0.870.710.940.710.96
Symptoms at 180-day visit13365C5.0CV0.6 [0.22–0.93]0.2 [-0.51–0.87]0.570.610.58
Symptoms at 180-day visit13365C5.0Training0.930.860.960.890.97
Symptoms at 180-day visit13365ensembleCV0.58 [0.41–0.74]0.16 [-0.19–0.49]0.60.520.63
Symptoms at 180-day visit13365ensembleTraining0.990.9810.981
Symptoms at 180-day visit13365glmnetCV0.56 [0.17–0.86]0.13 [-0.64–0.72]0.560.540.58
Symptoms at 180-day visit13365glmnetTraining0.850.70.920.820.88
Symptoms at 180-day visit13365nnetCV0.59 [0.29–0.86]0.17 [-0.52–0.72]0.580.60.57
Symptoms at 180-day visit13365nnetTraining11111
Symptoms at 180-day visit13365rfCV0.56 [0.29–0.86]0.13 [-0.46–0.71]0.590.560.56
Symptoms at 180-day visit13365rfTraining11111
Symptoms at 180-day visit13365svmRadialCV0.54 [0.17–0.83]0.089 [-0.67–0.67]0.550.450.62
Symptoms at 180-day visit13365svmRadialTraining0.860.730.940.850.88
  1. AUC = area under the curve; CT = computed tomography; glmnet = elastic-net regularized generalized linear models; nnet = neural networks; svmRadial = support vector machines with radial basis function kernel; rf = random forest; ensemble = model ensemble with elastic-net regularized generalized linear models

Appendix 1—table 6
Performance of machine learning classifiers in the acute COVID-19 severity strata.

Outcome: outcome variable at the 180-day follow-up visit; cohort subset: cohort acute COVID-19 severity strata (mild–moderate: outpatient or hospitalized without oxygen; severe–critical: oxygen therapy or ICU),

OutcomeCohort subsetTotal NEvents NMethodData setAUCSensitivitySpecificity
CT abnormalities at 180-day visitWhole cohort10949C5.0Training111
CT abnormalities at 180-day visitMild–moderate COVID-195818C5.0Training111
CT abnormalities at 180-day visitSevere–critical COVID-195131C5.0Training111
CT abnormalities at 180-day visitWhole cohort10949rfTraining111
CT abnormalities at 180-day visitMild–moderate COVID-195818rfTraining111
CT abnormalities at 180-day visitSevere–critical COVID-195131rfTraining111
CT abnormalities at 180-day visitWhole cohort10949svmRadialTraining0.930.840.87
CT abnormalities at 180-day visitMild–moderate COVID-195818svmRadialTraining0.90.610.95
CT abnormalities at 180-day visitSevere–critical COVID-195131svmRadialTraining0.960.970.7
CT abnormalities at 180-day visitWhole cohort10949nnetTraining0.7810.57
CT abnormalities at 180-day visitMild–moderate COVID-195818nnetTraining0.9210.85
CT abnormalities at 180-day visitSevere–critical COVID-195131nnetTraining0.510
CT abnormalities at 180-day visitWhole cohort10949glmnetTraining111
CT abnormalities at 180-day visitMild–moderate COVID-195818glmnetTraining111
CT abnormalities at 180-day visitSevere–critical COVID-195131glmnetTraining111
CT abnormalities at 180-day visitWhole cohort10949ensembleTraining0.980.860.98
CT abnormalities at 180-day visitMild–moderate COVID-195818ensembleTraining0.980.611
CT abnormalities at 180-day visitSevere–critical COVID-195131ensembleTraining110.95
CT severity score >5 at 180-day visitWhole cohort10921C5.0Training0.70.430.98
CT severity score >5 at 180-day visitMild–moderate COVID-19586C5.0Training0.570.170.98
CT severity score >5 at 180-day visitSevere–critical COVID-195115C5.0Training0.750.530.97
CT severity score >5 at 180-day visitWhole cohort10921rfTraining111
CT severity score >5 at 180-day visitMild–moderate COVID-19586rfTraining111
CT severity score >5 at 180-day visitSevere–critical COVID-195115rfTraining111
CT severity score >5 at 180-day visitWhole cohort10921svmRadialTraining0.990.571
CT severity score >5 at 180-day visitMild–moderate COVID-19586svmRadialTraining0.980.171
CT severity score >5 at 180-day visitSevere–critical COVID-195115svmRadialTraining10.731
CT severity score >5 at 180-day visitWhole cohort10921nnetTraining10.951
CT severity score >5 at 180-day visitMild–moderate COVID-19586nnetTraining10.831
CT severity score >5 at 180-day visitSevere–critical COVID-195115nnetTraining111
CT severity score >5 at 180-day visitWhole cohort10921glmnetTraining0.970.711
CT severity score >5 at 180-day visitMild–moderate COVID-19586glmnetTraining0.940.331
CT severity score >5 at 180-day visitSevere–critical COVID-195115glmnetTraining10.871
CT severity score >5 at 180-day visitWhole cohort10921ensembleTraining0.650.480.99
CT severity score >5 at 180-day visitMild–moderate COVID-19586ensembleTraining0.380.170.98
CT severity score >5 at 180-day visitSevere–critical COVID-195115ensembleTraining0.740.61
Symptoms at 180-day visitWhole cohort13365C5.0Training0.960.890.97
Symptoms at 180-day visitMild–moderate COVID-196430C5.0Training0.970.91
Symptoms at 180-day visitSevere–critical COVID-196935C5.0Training0.960.890.94
Symptoms at 180-day visitWhole cohort13365rfTraining111
Symptoms at 180-day visitMild–moderate COVID-196430rfTraining111
Symptoms at 180-day visitSevere–critical COVID-196935rfTraining111
Symptoms at 180-day visitWhole cohort13365svmRadialTraining0.940.850.88
Symptoms at 180-day visitMild–moderate COVID-196430svmRadialTraining0.930.770.85
Symptoms at 180-day visitSevere–critical COVID-196935svmRadialTraining0.950.910.91
Symptoms at 180-day visitWhole cohort13365nnetTraining111
Symptoms at 180-day visitMild–moderate COVID-196430nnetTraining111
Symptoms at 180-day visitSevere–critical COVID-196935nnetTraining111
Symptoms at 180-day visitWhole cohort13365glmnetTraining0.920.820.88
Symptoms at 180-day visitMild–moderate COVID-196430glmnetTraining0.910.730.88
Symptoms at 180-day visitSevere–critical COVID-196935glmnetTraining0.920.890.88
Symptoms at 180-day visitWhole cohort13365ensembleTraining10.981
Symptoms at 180-day visitMild–moderate COVID-196430ensembleTraining10.971
Symptoms at 180-day visitSevere–critical COVID-196935ensembleTraining111
Lung function impairment at 180-day visitWhole cohort11138C5.0Training0.850.790.9
Lung function impairment at 180-day visitMild–moderate COVID-195514C5.0Training0.810.710.9
Lung function impairment at 180-day visitSevere–critical COVID-195624C5.0Training0.870.830.91
Lung function impairment at 180-day visitWhole cohort11138rfTraining111
Lung function impairment at 180-day visitMild–moderate COVID-195514rfTraining111
Lung function impairment at 180-day visitSevere–critical COVID-195624rfTraining111
Lung function impairment at 180-day visitWhole cohort11138svmRadialTraining0.940.710.96
Lung function impairment at 180-day visitMild–moderate COVID-195514svmRadialTraining0.880.50.98
Lung function impairment at 180-day visitSevere–critical COVID-195624svmRadialTraining0.980.830.94
Lung function impairment at 180-day visitWhole cohort11138nnetTraining0.820.791
Lung function impairment at 180-day visitMild–moderate COVID-195514nnetTraining0.70.641
Lung function impairment at 180-day visitSevere–critical COVID-195624nnetTraining0.890.881
Lung function impairment at 180-day visitWhole cohort11138glmnetTraining0.890.610.95
Lung function impairment at 180-day visitMild–moderate COVID-195514glmnetTraining0.840.290.95
Lung function impairment at 180-day visitSevere–critical COVID-195624glmnetTraining0.910.790.94
Lung function impairment at 180-day visitWhole cohort11138ensembleTraining0.980.790.95
Lung function impairment at 180-day visitMild–moderate COVID-195514ensembleTraining0.970.710.95
Lung function impairment at 180-day visitSevere–critical COVID-195624ensembleTraining0.980.830.94
CT abnormalities at 180-day visitWhole cohort10949C5.0CV0.780.690.74
CT abnormalities at 180-day visitMild–moderate COVID-195818C5.0CV0.690.430.8
CT abnormalities at 180-day visitSevere–critical COVID-195131C5.0CV0.780.850.62
CT abnormalities at 180-day visitWhole cohort10949rfCV0.780.720.74
CT abnormalities at 180-day visitMild–moderate COVID-195818rfCV0.760.430.88
CT abnormalities at 180-day visitSevere–critical COVID-195131rfCV0.710.880.47
CT abnormalities at 180-day visitWhole cohort10949svmRadialCV0.80.780.73
CT abnormalities at 180-day visitMild–moderate COVID-195818svmRadialCV0.750.560.9
CT abnormalities at 180-day visitSevere–critical COVID-195131svmRadialCV0.760.920.4
CT abnormalities at 180-day visitWhole cohort10949nnetCV0.690.710.64
CT abnormalities at 180-day visitMild–moderate COVID-195818nnetCV0.670.590.77
CT abnormalities at 180-day visitSevere–critical COVID-195131nnetCV0.620.780.39
CT abnormalities at 180-day visitWhole cohort10949glmnetCV0.790.710.72
CT abnormalities at 180-day visitMild–moderate COVID-195818glmnetCV0.780.660.78
CT abnormalities at 180-day visitSevere–critical COVID-195131glmnetCV0.750.750.6
CT abnormalities at 180-day visitWhole cohort10949ensembleCV0.810.750.8
CT abnormalities at 180-day visitMild–moderate COVID-195818ensembleCV0.760.550.92
CT abnormalities at 180-day visitSevere–critical COVID-195131ensembleCV0.790.870.55
CT severity score >5 at 180-day visitWhole cohort10921C5.0CV0.70.390.98
CT severity score >5 at 180-day visitMild–moderate COVID-19586C5.0CV0.550.130.98
CT severity score >5 at 180-day visitSevere–critical COVID-195115C5.0CV0.760.490.97
CT severity score >5 at 180-day visitWhole cohort10921rfCV0.730.40.95
CT severity score >5 at 180-day visitMild–moderate COVID-19586rfCV0.580.0330.96
CT severity score >5 at 180-day visitSevere–critical COVID-195115rfCV0.760.550.93
CT severity score >5 at 180-day visitWhole cohort10921svmRadialCV0.750.480.97
CT severity score >5 at 180-day visitMild–moderate COVID-19586svmRadialCV0.590.130.97
CT severity score >5 at 180-day visitSevere–critical COVID-195115svmRadialCV0.790.610.97
CT severity score >5 at 180-day visitWhole cohort10921nnetCV0.720.470.87
CT severity score >5 at 180-day visitMild–moderate COVID-19586nnetCV0.570.170.89
CT severity score >5 at 180-day visitSevere–critical COVID-195115nnetCV0.760.590.84
CT severity score >5 at 180-day visitWhole cohort10921glmnetCV0.760.410.94
CT severity score >5 at 180-day visitMild–moderate COVID-19586glmnetCV0.630.170.97
CT severity score >5 at 180-day visitSevere–critical COVID-195115glmnetCV0.780.510.89
CT severity score >5 at 180-day visitWhole cohort10921ensembleCV0.750.450.98
CT severity score >5 at 180-day visitMild–moderate COVID-19586ensembleCV0.640.170.98
CT severity score >5 at 180-day visitSevere–critical COVID-195115ensembleCV0.780.570.99
Symptoms at 180-day visitWhole cohort13365C5.0CV0.570.610.58
Symptoms at 180-day visitMild–moderate COVID-196430C5.0CV0.580.620.56
Symptoms at 180-day visitSevere–critical COVID-196935C5.0CV0.550.60.6
Symptoms at 180-day visitWhole cohort13365rfCV0.590.560.56
Symptoms at 180-day visitMild–moderate COVID-196430rfCV0.60.610.55
Symptoms at 180-day visitSevere–critical COVID-196935rfCV0.570.520.58
Symptoms at 180-day visitWhole cohort13365svmRadialCV0.550.450.62
Symptoms at 180-day visitMild–moderate COVID-196430svmRadialCV0.540.480.59
Symptoms at 180-day visitSevere–critical COVID-196935svmRadialCV0.560.430.66
Symptoms at 180-day visitWhole cohort13365nnetCV0.580.60.57
Symptoms at 180-day visitMild–moderate COVID-196430nnetCV0.580.630.54
Symptoms at 180-day visitSevere–critical COVID-196935nnetCV0.580.580.6
Symptoms at 180-day visitWhole cohort13365glmnetCV0.560.540.58
Symptoms at 180-day visitMild–moderate COVID-196430glmnetCV0.560.570.6
Symptoms at 180-day visitSevere–critical COVID-196935glmnetCV0.550.510.56
Symptoms at 180-day visitWhole cohort13365ensembleCV0.60.520.63
Symptoms at 180-day visitMild–moderate COVID-196430ensembleCV0.610.570.63
Symptoms at 180-day visitSevere–critical COVID-196935ensembleCV0.60.490.63
Lung function impairment at 180-day visitWhole cohort11138C5.0CV0.70.540.84
Lung function impairment at 180-day visitMild–moderate COVID-195514C5.0CV0.610.370.86
Lung function impairment at 180-day visitSevere–critical COVID-195624C5.0CV0.750.630.81
Lung function impairment at 180-day visitWhole cohort11138rfCV0.720.490.85
Lung function impairment at 180-day visitMild–moderate COVID-195514rfCV0.580.260.9
Lung function impairment at 180-day visitSevere–critical COVID-195624rfCV0.790.620.79
Lung function impairment at 180-day visitWhole cohort11138svmRadialCV0.690.50.84
Lung function impairment at 180-day visitMild–moderate COVID-195514svmRadialCV0.560.290.88
Lung function impairment at 180-day visitSevere–critical COVID-195624svmRadialCV0.750.620.79
Lung function impairment at 180-day visitWhole cohort11138nnetCV0.590.440.76
Lung function impairment at 180-day visitMild–moderate COVID-195514nnetCV0.470.290.83
Lung function impairment at 180-day visitSevere–critical COVID-195624nnetCV0.620.520.67
Lung function impairment at 180-day visitWhole cohort11138glmnetCV0.660.510.86
Lung function impairment at 180-day visitMild–moderate COVID-195514glmnetCV0.550.210.88
Lung function impairment at 180-day visitSevere–critical COVID-195624glmnetCV0.730.680.83
Lung function impairment at 180-day visitWhole cohort11138ensembleCV0.720.480.89
Lung function impairment at 180-day visitMild–moderate COVID-195514ensembleCV0.590.260.92
Lung function impairment at 180-day visitSevere–critical COVID-195624ensembleCV0.780.610.85
  1. AUC = area under the curve; CT = computed tomography; ICU = intensive care unit; glmnet = elastic-net regularized generalized linear models; nnet = neural network; svmRadial = support vector machines with radial basis function kernel; rf = random forest; ensemble = model ensemble with elastic-net regularized generalized linear models

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  1. Thomas Sonnweber
  2. Piotr Tymoszuk
  3. Sabina Sahanic
  4. Anna Boehm
  5. Alex Pizzini
  6. Anna Luger
  7. Christoph Schwabl
  8. Manfred Nairz
  9. Philipp Grubwieser
  10. Katharina Kurz
  11. Sabine Koppelstätter
  12. Magdalena Aichner
  13. Bernhard Puchner
  14. Alexander Egger
  15. Gregor Hoermann
  16. Ewald Wöll
  17. Günter Weiss
  18. Gerlig Widmann
  19. Ivan Tancevski
  20. Judith Löffler-Ragg
(2022)
Investigating phenotypes of pulmonary COVID-19 recovery: A longitudinal observational prospective multicenter trial
eLife 11:e72500.
https://doi.org/10.7554/eLife.72500