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A novel haemocytometric COVID-19 prognostic score developed and validated in an observational multicentre European hospital-based study

  1. Joachim Linssen
  2. Anthony Ermens
  3. Marvin Berrevoets
  4. Michela Seghezzi
  5. Giulia Previtali
  6. Simone van der Sar-van der Brugge
  7. Henk Russcher
  8. Annelies Verbon
  9. Judith Gillis
  10. Jürgen Riedl
  11. Eva de Jongh
  12. Jarob Saker
  13. Marion Münster
  14. Imke CA Munnix
  15. Anthonius Dofferhof
  16. Volkher Scharnhorst
  17. Heidi Ammerlaan
  18. Kathleen Deiteren
  19. Stephan JL Bakker
  20. Lucas Joost Van Pelt
  21. Yvette Kluiters-de Hingh
  22. Mathie PG Leers
  23. Andre J van der Ven  Is a corresponding author
  1. Sysmex Europe GmbH, Germany
  2. Amphia Hospital, Netherlands
  3. Elisabeth-Tweesteden Hospital, Netherlands
  4. Hospital Papa Giovanni XXIII, Italy
  5. Erasmus MC, University Medical Center, Netherlands
  6. Leiden University Medical Center, Netherlands
  7. Albert Schweitzer Hospital, Netherlands
  8. Canisius Wilhelmina Hospital, Netherlands
  9. Catharina Hospital, Netherlands
  10. University Hospital Antwerp, Belgium
  11. University Medical Center Groningen, University of Groningen, Netherlands
  12. Zuyderland Medical Center, Netherlands
  13. Radboud University Medical Center, Netherlands
Research Article
Cite this article as: eLife 2020;9:e63195 doi: 10.7554/eLife.63195
12 figures, 7 tables and 5 additional files

Figures

Patient flow chart from prognostic score development and validation cohorts, including sample numbers for CBC-Diff (with or without RET) and clinical outcome.

Footnote. (a) Details of how the validation patient cohort patients were selected are provided in Figure 10 , (b) the exclusion criteria for the validation cohort were the same as for the development patient cohort.

Clinical severity and outcome by age of all patients.
Figure 2—source data 1

Source data for clinical severity and outcome by age of all patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig2-data1-v2.csv
Trends of lymphocyte-related parameters over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

Note: 14 days of hospitalisation refers to Day 0 (day of admission) plus the next 13 days after admission. The normal reference range is depicted by the area between the dotted horizontal lines. Vertical bars indicate standard error of the mean (SEM). (A) Absolute lymphocyte count (LYMPH), (B) neutrophil-to-lymphocyte ratio (NLR), (C) antibody-synthesising lymphocytes as percentage of lymphocytes (AS-LYMPH%/L), (D) reactive lymphocytes minus AS-LYMPH (as a percentage of lymphocytes). The number of sample measurements available per day for the trend analysis for the parameters plotted per patient group are shown in Figure 3—source data 1.

Figure 3—source data 1

Source data for number of measurements for each day of hospitalisation that were available per patient group for the trends of lymphocyte-related parameters over 14 days of hospitalisation.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig3-data1-v2.xlsx
Figure 3—source data 2

Source data for trends of absolute lymphocyte count over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig3-data2-v2.csv
Figure 3—source data 3

Source data for trends of neutrophil-to-lymphocyte ratio over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig3-data3-v2.csv
Figure 3—source data 4

Source data for trends of AS-LYMPH%/L over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig3-data4-v2.csv
Figure 3—source data 5

Source data for trends of RE-Lymph minus AS-LYMPH as a percentage of total lymphocytes over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig3-data5-v2.csv
Trends of neutrophil-related parameters over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

Note: 14 days refers to day 0 (day of admission) plus the next 13 days after admission. The normal reference range is depicted by the area between the dotted horizontal lines. Vertical bars indicate standard error of the mean (SEM). (A) Absolute neutrophil count (NEUT), (B) neutrophil reactivity index (NEUT-RI), (C) immature granulocytes (IG), (D) Immature granulocyte-to-lymphocyte ratio *100 (IGLR). The number of sample measurements available per day for the trend analysis for the parameters plotted per patient group are shown in Figure 4—source data 1.

Figure 4—source data 1

Source data for number of measurements for each day of hospitalisation that were available per patient group for the trends of neutrophil-related parameters over 14 days of hospitalisation.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig4-data1-v2.xlsx
Figure 4—source data 2

Source data for trends of absolute neutrophil count over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig4-data2-v2.csv
Figure 4—source data 3

Source data for trends of NEUT-RI over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig4-data3-v2.csv
Figure 4—source data 4

Source data for trends of immature granulocyte count over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig4-data4-v2.csv
Figure 4—source data 5

Source data for trends of immature granuclocyte-to-lymphocyte ratio over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig4-data5-v2.csv
Trends of monocyte parameters over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

Note: 14 days of hospitalisation refers to day 0 (day of admission) plus the first 13 days after admission. The normal reference range is depicted by the area between the dotted horizontal lines. Vertical bars indicate standard error of the mean (SEM). (A) Absolute monocyte count (MONO), (B) reactive monocytes as a percentage of monocytes (RE-MONO%/M). The number of sample measurements available per day for the trend analysis for the parameters plotted per patient group are shown in Figure 5—source data 1.

Figure 5—source data 1

Source data for number of measurements for each day of hospitalisation that were available per patient group for the trends of monocyte parameters over 14 days of hospitalisation.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig5-data1-v2.xlsx
Figure 5—source data 2

Source data for trends of absolute monocyte count over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig5-data2-v2.csv
Figure 5—source data 3

Source data of trends of reactive monocytes as a percentage of total monocyte count over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig5-data3-v2.csv
Trends of red blood cell-related parameters over 14 days of hospitalisation in critical illness (C) and non-critical (NC) patients.

Note: 14 days of hospitalisation refers to day 0 (day of admission) plus the first 13 days after admission. The normal reference range is depicted by the area between the dotted horizontal lines. Vertical bars indicate standard error of the mean (SEM). (A) Haemoglobin (HGB) corrected for age and gender, (B) reticulocyte count (RET), (C) difference in haemoglobinisation of reticulocytes and red blood cells (DELTA-He), (D) nucleated red blood cells (NRBC). The number of sample measurements available per day for the trend analysis for the parameters plotted per patient group are shown in Figure 6—source data 1.

Figure 6—source data 1

Source data for number of measurements for each day of hospitalisation that were available per patient group for the trends of red blood cell-related parameters over 14 days of hospitalisation.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig6-data1-v2.xlsx
Figure 6—source data 2

Source data for trends of corrected haemoglobin values over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig6-data2-v2.csv
Figure 6—source data 3

Source data for trends of absolute reticulocyte count over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig6-data3-v2.csv
Figure 6—source data 4

Source data for trends of Delta-He values over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig6-data4-v2.csv
Figure 6—source data 5

Source data for trends of nucleated red blood cell counts over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig6-data5-v2.csv
Trends of platelet parameters over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

Note: 14 days refers to day 0 (day of admission) plus the first 13 days after admission. The normal reference range is depicted by the area between the dotted horizontal lines. Vertical bars indicate standard error of the mean (SEM). (A) Platelet count (PLT), (B) platelet-to-lymphocyte ratio (PLR), (C) immature platelet count (IPF#) (D) immature platelet fraction (IPF%). The number of sample measurements available per day for the trend analysis for the parameters plotted per patient group are shown in Figure 7—source data 1.

Figure 7—source data 1

Source data for number of measurements for each day of hospitalisation that were available per patient group for the trends of platelet parameters over 14 days of hospitalisation.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig7-data1-v2.xlsx
Figure 7—source data 2

Source data for trends of platelet count over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig7-data2-v2.csv
Figure 7—source data 3

Source data for trends of platelet-to-lymphocyte count ratio over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig7-data3-v2.csv
Figure 7—source data 4

Source data for trends of absolute immature platelet count (IPF#) over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig7-data4-v2.csv
Figure 7—source data 5

Source data for trends of immature platelet fraction (IPF%) over 14 days of hospitalisation in critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig7-data5-v2.csv
Haemocytometric COVID-19 prognostic score prediction of clinical severity in the development cohort.

(A) Development cohort prognostic score 14-day hospitalisation time horizon (day of admission plus the first 13 days thereafter) comparing non-critical (NC) and critical illness (CI) groups. Points shown are mean values with vertical bars representing SEM (B) development cohort prognostic score 7-day hospitalisation time horizon comparing outcomes for the critical illness group (recovered with ICU or died) and the non-critical group (recovered without ICU). Points shown are mean values with vertical bars representing SEM, (C) ROC curve to compare the capability of prediction of critical illness disease progression of the prognostic score, absolute lymphocyte count (LYMPH#), neutrophil-to-lymphocyte ratio (NLR), absolute monocyte count (MONO#), platelet count (PLT) and platelet-to-lymphocyte ratio (PLR) for development cohort incorporating all measurements over the initial 14-day period of hospitalisation. The number of measurements for each day of hospitalisation that were available per patient group are shown in Figure 8—source data 1. There were markedly fewer measurements for the second week, notably in the NC group which may have contributed to bias.

Figure 8—source data 1

Source data for number of measurements for each day of hospitalisation that were available per patient group for prognostic score prediction of clinical severity in the development cohort.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig8-data1-v2.xlsx
Figure 8—source data 2

Source data for development cohort prognostic score 14-day hospitalisation time horizon (day of admission plus the first 13 days thereafter) comparing non-critical (NC) and critical illness (CI) groups.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig8-data2-v2.csv
Figure 8—source data 3

Source data for development cohort prognostic score 7-day hospitalisation time horizon comparing outcomes (recovered without ICU, recovered with ICU or died).

https://cdn.elifesciences.org/articles/63195/elife-63195-fig8-data3-v2.csv
Figure 8—source data 4

Source data for ROC curves to assess the capability of prediction of critical illness disease progression of the prognostic score, absolute lymphocyte count (LYMPH), neutrophil-to-lymphocyte ratio (NLR), absolute monocyte count (MONO), platelet count (PLT), and platelet-to-lymphocyte ratio (PLR) for development cohort incorporating all measurements over the initial 14-day period of hospitalisation.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig8-data4-v2.csv
Impact of age and presence of comorbidities on prediction of disease severity.

(A) Box and whisker plots of prognostic score values for NC and CI groups segregated by age. The prognostic score can predict severity independent of age, therefore potentially assisting in identifying young patients at risk for severe disease progression as well as older patients not at risk. (B) Box and whisker plots of prognostic score values for NC and CI groups segregated by comorbidities in the 75-84-year-old group, as an illustrative example. The prognostic score is significantly higher in patients with severe disease progression independent of the presence of comorbidities. Please refer to Table 6 for more detailed information on all age groups.

Figure 9—source data 1

Impact of age on prediction of disease severity.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig9-data1-v2.csv
Flow chart showing inclusion and exclusion of validation cohort patient.

Abbreviations: NC, non-critical patient group; CI, critical illness patient group. (a) The following criteria were used to ensure selection of only those patients for whom the primary presentation at hospital was related to COVID-19: Emergency department location on day 0, provisional diagnosis of pneumonia, if admitted, with admission to a general ward, internal medicine, ICU or anaesthesia (critical care).

Haemocytometric COVID-19 prognostic score prediction of clinical severity in the validation cohort.

(A) Validation cohort prognostic score 14-day hospitalisation time horizon comparing non-critical (NC) and critical illness (CI) groups, (B) ROC curve comparisons of prognostic score and NLR over 14 days. The prognostic score AUC (0.838, 95%CI 0.809-0.864) was significantly higher (P<0.0001) than the NLR AUC (0.673,95% CI 0.637-0.707). The number of measurements for each day of hospitalisation that were available per patient group are shown in Figure 11—source data 1. Overall, there were relatively few measurements per day for the NC group which has contributed to greater variance per time point.

Figure 11—source data 1

Source data for number of measurements for each day of hospitalisation that were available per patient group for prognostic score prediction of clinical severity in the validation cohort.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig11-data1-v2.xlsx
Figure 11—source data 2

Source data for haemocytometric COVID-19 prognostic score prediction of clinical severity in the validation cohort over 14 day hospitalisation time horizon comparing non-critical (NC) and critical illness (CI) groups.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig11-data2-v2.csv
Figure 11—source data 3

Source data for ROC curve comparisons of prognostic score and NLR over 14 days.

https://cdn.elifesciences.org/articles/63195/elife-63195-fig11-data3-v2.csv
Flow chart illustrating steps involved in prognostic score development.

Abbreviations: NC, non-critical patient group; CI, critical illness patient group; ROC, receiver operating characteristics (curve); AUC, area under the curve.

Tables

Table 1
Basic demographic characteristics of COVID-19 PCR confirmed patients enrolled for prognostic score development.
TotalMildModerateSevereCriticalFatal
All patients
n [%]
98264 [6.5]198 [20.2]323 [32.9]144 [14.7]253 [25.8]
Age Years (range)18–9618–9622–9119–9328–8842–95
Age Years (median)71596869,56579
Females
n [%]314 [32.0]27 [8.6]74 [23.6]113 [36.0]38 [12.1]62 [19.7]
Age Years (range)18–9518–9222–8619–9328–8156–95
Age Years (median)696267696479.5
Males
n, [%]668 [68.0]37 [5.5]124 [18.6]210 [31.4]106 [15.9]191 [28.6]
Age Years (range)26–9635–9630–9126–8932–8842–93
Age Years (median)72596869.56579
Length of hospitalisation
Days (range)0–7801–56–462–781–44
Days (median)60310226
Comorbidities*
Absent [%][27][68][45][35][24][13]
Present [%][73][32][55][65][76][87]
Diabetes [%][15.9][5.5][15.0][14.9][20.5][18.2]
Hypertension [%][12.8][1.8][7.9][14.5][17.9][13.9]
Cardiovascular disorders [%][27.6][16.3][21.3][25.6][18.8][41.6]
Respiratory disorders [%][12.0][5.5][8.7][12.6][12.5][14.8]
CNS disorders [%][4.3][3.6][3.2][4.6][1.8][6.2]
Renal disorders [%][4.8][1.8][3.9][5.0][5.4][5.7]
Malignancy [%][9.2][0][9.5][8.4][9.8][12.0]
Autoimmune disease [%][3.7][5.5][3.9][2.3][6.3][3.3]
Pregnancy [%][0.3][1.8][0.8][0][0][0]
Obesity§ [%][2.7][0][3.1][3.4][1.8][2.9]
Other [%][7.8][5.5][4.7][10.7][12.5][4.3]
  1. * Occurrence of comorbidities is shown as a relative frequency expressed as a percentage (patients with a comorbidity divided by total number of patients in whom the presence or absence of comorbidities was recorded) as 2 of the participating study centres did not document the presence or absence of comorbidities.

    † Absent – comorbidities confirmed to be absent.

  2. ‡ Present – one or more comorbidities confirmed to be present.

    § Body mass index (BMI) measurements were not undertaken as part of this study. It was also up to the discretion of the physician to document obesity as a comorbidity. As this study was undertaken in the early phase of the pandemic, it may not have been common knowledge to all attending physicians that obesity is significant contributor to adverse outcomes in COVID-19.

  3. ¶ Other includes gastrointestinal disorders, musculoskeletal disorders, endocrine disorders, lipid disorders, haemochromatosis psoriasis, malnutrition, and Down syndrome.

Table 1—source data 1

Source data for basic demographic characteristics of COVID-19 PCR confirmed patients enrolled for prognostic score development.

https://cdn.elifesciences.org/articles/63195/elife-63195-table1-data1-v2.csv
Table 2
Demographic and first haemocytometric data at hospital presentation or within 3 days after admission.
Non-critical
group (NC)
Critical illness
group (CI)
P valueAll patientsReference values
healthy volunteers
% abnormal
results
Patients [n]557366<0.0001923
Female [n]20191<0.0001292
Male [n]356276<0.0001631
Age (Years, median)6574<0.000168
Female [Y, median]64730.004067
Male [Y, median]66740.001069
Female vs. Male in NC [n] [F, M][201, 356]nansna
Female vs. Male in CI [n] [F, M]na[91, 276]nsna
Duration of symptoms [Days, median]77ns7
Haemocytometry
Patients/healthy volunteers, [samples]557, [899]366, [688]923, [1587]12782
White blood cells findingsMedian [95% CI]Median [95% CI]P valueMedian [95% CI]Median [95% CI]%
WBC (white blood cell count) [10³/µL]5.92 [2.42–13.17]7.75 [3.02–18.61]<0.00016.43 [2.59–16.10]5.84 [3.64–9.61]28.4
NEUT (neutrophil count) [10³/µL]4.37 [1.39–11.21]6.25 [2.17–15.18]<0.00014.96 [1.53–13.61]3.12 [1.62–5.86]41.4
IG (immature granulocyte count) [10³/µL]0.04 [0.01–0.26]0.06 [0.01–0.67]<0.00010.05 [0.01–0.48]0.03 [0.01–0.09]16.3
LYMPH (lymphocyte count) [10³/µL]0.91 [0.35–2.09]0.74 [0.26–1.91]<0.00010.78 [0.28–2.00]1.92 [1.07–3.41]70.5
NLR (neutrophil-to-lymphocyte ratio) [ratio]4.7 [1.3–17.7]8.1 [2.1–39.0]<0.00016.0 [1.4–28.5]1.6 [0.8–3.6]77.1
IGLR (immature granulocyte-to-lymphocyte ratio) [ratio*100]3.9 [0.8–36.1]7.3 [1.2–69.1]<0.00014.8 [0.81–52.7]1.8 [0.5–4.8]49.4
MONO (monocyte count) [10³/µL]0.43 [0.13–1.29]0.43 [0.10–1.22]0.01720.42 [0.11–1.27]0.48 [0.28–0.83]22.8
EO (eosinophil count) [10³/µL]0.01 [0.00–0.26]0.01 [0.00–0.31]ns.0.01 [0.00–0.29]0.16 [0.04–0.47]76.6
BASO (basophil count) [10³/µL]0.01 [0.00–0.05]0.01 [0.00–0.08]ns.0.01 [0.00–0.07]0.04 [0.02–0.09]56.1
WBC extended parameters
NEUT-RI (neutrophil reactivity index) [FI]50.0 [43.9–57.0]50.6 [44.2–59.2]0.002350.2 [44.0–58.1]46.1 [41.9–50.6]47.0
NEUT-GI (neutrophil granularity index) [GI]153 [143–163]153 [141–163]ns153 [143–163]149 [142–157]23.2
RE-LYMPH (reactive lymphocytes as % of lymphocytes) [% of lymph]9.9 [2.6–23.6]10.0 [2.4–28.9]<0.000110.5 [2.5–26.3]3.3 [1.3–7.6]73.3
AS-LYMPH (antibody-synthesising lymphocytes as % of lymphocytes) [% of lymph]3.6 [0.0–13.2]4.2 [0.0–19.8]<0.00013.8 [0.0–17.4]0.0 [0.0–0.0]90.4
RE-MONO (reactive monocytes as % of monocytes) [% of mono]2.5 [0.2–17.9]3.9 [0.0–30.0]<0.00013.0 [0.3–22.7]0.0 [0.0–4.3]37.3
Red blood cells findings
HGB (haemoglobin) [g/dL]13.4 [9.6–16.3]12.9 [8.4–16.5]<0.000113.2 [8.9–16.3]14.1 [11.9–16.6]26.5
RBC (red blood cell count) [106/µL]4.8 [3.10–5.54]4.31 [2.90–5.62]<0.00014.42 [3.00–5.58]4,73 [3.99–5.60]26.8
MCV (mean cell volume) [fL]89.1 [78.3–101.6]90.2 [77.9–103.0]ns89.5 [78.3–101.9]90.1 [82.5–97.8]14.2
RET (reticulocyte count) [10³/µL]30.2 [14.1–80.0]30.0 [13.9–95.6]ns30.1 [14.1–89.5]57.5 [32.6–96.6]55.5
NRBC (nucleated red blood cell count) [/µL]0 [0–10]0 [0–60]<0.00010 [0–30]0 [0–10]46
RET-He (reticulocyte haemoglobin equivalent) [pg]30.2 [23.6–35.5]29.4 [22.9–34.8]ns29.9 [23.1–35.2]32.8 [29.4–35.4]44.4
RBC extended parameters
DELTA-He (difference in reticulocyte and RBC haemoglobin content) [pg]−0.5 [−4.8–3.1]−1.2 [−7.0–3.1]<0.0001−0.7 [−5.9–3.1]2.6 [1.4–3.6]85.7
MICRO-R (% of RBC that are microcytic) [%]1.5 [0.4–8.5]1.5 [0.4–10.0]ns1.5 [0.4–9.5]1.1 [0.3–4.2]9.9
HYPO-He (% of RBC that are hypochromic) [%]0.2 [0.1–2.0]0.3 [0.1–2.6]<0.00010.2 [0.1–2.5]0.1 [0.0–0.5]21.9
Platelet findings
PLT (platelet count) [10³/µL]199 [96–451]205 [64–435]ns201 [79–446]256 [161–385]32.7
IPF% (immature platelet fraction) [%]4.3 [1.7–12.9]4.9 [2.0–5.9]ns4.5 [1.7–14.2]3.0 [1.1–8.1]14.6
PLT extended parameters
IPF# (absolute immature platelet count) [10³/µL]9.4 [3.6–30.9]11.2 [3.5–28.7]0.000110.2 [3.5–29.6]7.9 [3.1–18.1]15.4
  1. Note: The expanded name of the haemocytometric parameters is shown in brackets in italics. The unit of measure for each parameter is shown in square brackets. A more detailed explanation of the haemocytometric parameters is provided in Table 7 .

    Abbreviations: na, not applicable; ns, not significant.

Table 2—source data 1

Source data for demographic and first haemocytometric data available for patients at hospital presentation or within 3 days after admission.

https://cdn.elifesciences.org/articles/63195/elife-63195-table2-data1-v2.csv
Table 3
Haemocytometric COVID-19 prognostic score cut-off values.
VariablePrecondition1 Point2 Points3 Points4 Points
Primary
Variables
IG/L*100IG* ≥ 0,09≥10≥20≥40≥45
NLRnone[<7,7 and LYMPH < 1,07 and N/L²≥7,5] or
[≥7,7 < 16,5 and LYMPH < 0,65]
[≥7,7 < 16,5 and LYMPH ≥ 0,65][≥7,7 < 16,5 and LYMPH ≥ 1,07]≥16,5
RE-MONO/M [%]none[≥5 < 15 and RE-MONO < 0,03][≥5 < 15 and Re-MONO ≥ 0,03]n/a≥15
AS-LYMPH/L [%]none[≥5 and LYMPH§ < 10]≥10n/a≥15
DELTA-He [pg]RET ≥ 6.0[< −1 ≥ −2] or [<0,4 ≥ −1 and RET ≥ 20.0][< −2 ≥ −4]n/a< −4
NRBC [/µL]HGB** ≥ 9
and
RET < 90
n/a≥ 20n/a≥40
Secondary VariablesHGB [g/dl]none≥17
HYPO-He [%]Micro-R†† < 10≥1,9
PLT [10³/µL]none<85
IPF# [10³/µL]none≥25
  1. Note: For the primary variables, one point = value above the cut-off value for the best AUC; two points = value above the cut-off value for the best AUC and ≥80% specificity; three points = value above the cut-off value for the best AUC and >90% specificity; and four points = value above the cut-off value for the best AUC and >95% specificity. The cut-off values for the secondary variables were chosen exclusively based on observed extremes of values in critical disease, with the maximum award of 1 point per variable.

    The prognostic score values were calculated automatically using a pre-set algorithm, using the above cut-off values to assign points per individual parameter. The aim is to have the formula for the calculation incorporated into the Laboratory Information System software in use in individual laboratories.

  2. Abbreviations: IGLR, immature granulocytes-to-lymphocyte ratio; NLR, neutrophil-to-lymphocyte ratio; AS-LYMPH%/L, antibody synthesising lymphocytes as a proportion of lymphocytes; RE-MONO%/M, reactive monocytes as a proportion of monocytes; DELTA-He, difference in haemoglobinisation of reticulocytes and red blood cells; NRBC, absolute nucleated red blood cell count; HGB, haemoglobin; HYPO-He, percentage of red blood cells that are hypochromic; PLT, platelet count; IPF, absolute immature platelet count; N/L2, neutrophil-to-lymphocyte squared ratio.

    * Unit of measure for IG (absolute immature granulocyte count) is x 103/µL.

  3. † Unit of measure for LYMPH (absolute lymphocyte count) is x 103/µL.

    ‡ Unit of measure for RE-MONO (absolute reactive monocyte count) is x 103/µL.

  4. § Unit of measure for LYMPH% (percentage lymphocyte count).

    ¶ Unit of measure for RET (absolute reticulocyte count) is x 103/µL.

  5. ** Unit of measure for HGB (haemoglobin) is g/dL.

    †† Unit of measure for Micro-R is %.

Table 4
Development cohort prognostic score values by day based on clinical severity group, initial management, and outcome.
Not hospitalisedHospitalised with admission to a general ward on day of initial presentation (non-ICU)Hospitalised with admission directly to ICU on day of initial presentation
dayMild
Median score*
nRecovered
Median score*
nDied
Median score*
nRecovered
Median score*
nDied
Median score*
n
00.5 (0.0–1.0)341.0 (1.0–2.0)2433.0 (2.0–4.0)864.0 (3.0–6.0)704.0 (2.6–8.4)21
12.0 (1.5–3.0)594.0 (1,5–6.7)156.5 (3.0–9.3)247.0 (1.5–14,1)10
22.0 (1.0–3.0)965.0 (4.0–6.0)237.0 (6.0–8.9)3712.5 (1.8–16.6)8
32.0 (1.0–3.0)755.0 (4.4–7.6)168.0 (7.0–9.0)3112.5 (7.8–18.3)8
43.0 (2.0–4.0)597.0 (6.0–8.7)158.0 (6.0–10.8)3015.0 (3.8–20.4)8
52.0 (1.0–3.0)3712.0 (6.5–14.9)136.5 (4.8–8.3)347.0 (0.8–19.1)8
63.0 (2.0–4.0)3711.0 (6.1–14.8)99.0 (7.0–11.0)2914.0 (na)5
72.0 (0.3–6.7)2311.0 (5.2–15.4)68.0 (6.0–11.2)298.0 (5.8–12.4)11
  1. Note: Recovered refers to patients that survived and were discharged from hospital. By definition, ‘Mild’ patients are not hospitalised and therefore only day 0 prognostic score values are available.

    * Median score refers to the median value obtained for the haemocytometric COVID-19 prognostic score for the patient group for patients with the same length of hospitalisation on the day of measurement. Values in brackets represent the 95% CI for the median.

  2. † Sample size was too small to calculate 95% CI.

Table 4—source data 1

Source data for development cohort prognostic score values by day based on clinical severity group, initial management, and outcome.

https://cdn.elifesciences.org/articles/63195/elife-63195-table4-data1-v2.csv
Table 5
Receiver Operator Characteristics (ROC) curve comparisons between the haemocytometric COVID-19 prognostic score versus other parameters.
Prognostic scoreLYMPH (x10³/µL)NLRMONO (x10³/µL)PLT (x10³/µL)PLR
Day* < 4 [n = 859]
[AUC]0.7530.5910.7090.5160.5370.602
[95% CI]0.723 to 0.7810.558 to 0.6240.678 to 0.7400.482 to 0.5500.503 to 0.5700.568 to 0.635
[cut-off value]>3<0.810>7.7<0.400>234>308
[P value vs prognostic score]na<0.00010.0066<0.0001<0.0001<0.0001
Day < 14 [n = 1423]
[AUC]0.8060.550.7180.5510.5630.591
[95% CI]0.784 to 0.8260.523 to 0.5760.694 to 0.7410.525 to 0.5770.537 to 0.5890.565 to 0.617
[cut-off value]>4<0.810>7.1>0.640>268>308
[P value vs prognostic score]na<0.0001<0.0001<0.0001<0.0001<0.0001
Day 0 [n = 454]
[AUC]0.7220.6030.6830.5060.5370.605
[95% CI]0.678 to 0.7630.556 to 0.6480.638 to 0.7260.459 to 0.5530.490 to 0.5840.558 to 0.650
[cut-off value]>3<0.780>7.6>0.700>234>375
[P value vs prognostic score]na0.00010.0660<0.0001<0.00010.0001
Day 1 [n = 109]
[AUC]0.7370.5570.6640.5110.5550.602
[95% CI]0.644 to 0.8170.459 to 0.6520.567 to 0.7510.413 to 0.6080.457 to 0.6510.504 to 0.695
[cut-off value]>4<0.620>11.6>0.180>218>358
[p value vs. prognostic score]na0.00360.11320.00120.00450.0265
Day 2 [n = 164]
[AUC]0.7390.5720.7140.5750.5150.526
[95% CI]0.665 to 0.8040.492 to 0.6490.638 to 0.7820.495 to 0.6520.436 to 0.5940.446 to 0.604
[cut-off value]>4<1.020>5.1<0.470<118>217
[P value vs prognostic score]na0.00060.47800.0026<0.00010.0001
Day 3 [n = 132]
[AUC]0.8750.6020.8270.5010.5820.647
[95% CI]0.806 to 0.9260.514 to 0.6860.751 to 0.8870.413 to 0.5900.493 to 0.6670.559 to 0.728
[cut-off value]>3<0.810>7,3<0.680>255>280
[p value vs prognostic score]na<0.00010.1860<0.0001<0.0001<0.0001
Day 4 [n = 112]
[AUC]0.8670.6040.7780.5720.5310.583
[95% CI]0.790 to 0.9240.507 to 0.6950.690 to 0.8510.475 to 0.6650.434 to 0.6260.486 to 0.676
[cut-off value]>4<0.710>7.7<0.270<238>330
[p value vs prognostic score]na<0.00010.0070<0.0001<0.0001<0.0001
Day 5 [n = 92]
[AUC]0.8770.5780.7530.5780.5990.506
[95% CI]0.792 to 0.9360.471 to 0.6800.652 to 0.8370.470 to 0.6800.492 to 0.7000.400 to 0.612
[cut-off value]>4<1.140>6.5<0.580<227<350
[p value vs prognostic score]na<0.00010.0030<0.0001<0.0001<0.0001
Day 6 [n = 80]
[AUC]0.8750.5170.6880.5110.5890.545
[95% CI]0.782 to 0.9380.403 to 0.6300.575 to 0.7870.397 to 0.6250.474 to 0.6980.430 to 0.657
[cut-off value]>4<1.620>7.0>0.640<277<153
[p value vs prognostic score]na<0.0001<0.0001<0.0001<0.0001<0.0001
Day 7 [n = 100]
[AUC]0.8560.6330.7240.5610.5960.549
[95% CI]0.772 to 0.9180.531 to 0.7270.625 to 0.8080.458 to 0.6600.493 to 0.6930.446 to 0.649
[cut-off value]>3<0.940>4.7<0.310<298>311
[p value vs prognostic score]na0.00020.0044<0.0001<0.0001<0.0001
  1. Note:”Prognostic score’ refers to the haemocytometric COVID-19 prognostic score comprised of NLR, IGLR, RE-MONO%/M, AS-LYMPH%/L, DELTA-He, NRBC, HGB, Hypo-He, PLT, and IPF#.

    Abbreviations: NLR, neutrophil-to-lymphocyte ratio; IGLR, immature granulocyte-to-lymphocyte ratio; RE-MONO%/M, reactive monocytes as percentage of total monocyte count; AS-LYMPH%/L, antibody-synthesising lymphocytes as percentage of total lymphocyte count; DELTA-He, difference in haemoglobinisation of reticulocytes and red blood cells; NRBC, absolute nucleated red blood cell count; HGB, haemoglobin; Hypo-He, percentage of red blood cells that are hypochromic; PLT, platelet count; IPF#, absolute immature platelet count; LYMPH, absolute lymphocyte count; MONO, absolute monocyte count; PLR, platelet-to-lymphocyte ratio; AUC, area under the curve; CI, confidence interval; na, not applicable.

  2. * ‘Day’ refers to the number of days of hospitalisation of patient at time of blood sample measurement. Day 0 refers to the day of first presentation at hospital.

    † ‘n’ refers to the number of complete profile (complete blood and differential count and reticulocyte channel) sample measurements available at a particular time point and included in the ROC curve analysis.

Table 5—source data 1

Source data for Receiver Operator Characteristics (ROC) curve comparisons between the haemocytometric COVID-19 prognostic score versus other parameters.

https://cdn.elifesciences.org/articles/63195/elife-63195-table5-data1-v2.csv
Table 6
Mann-Whitney test for significance of the difference in prognostic score between critical illness (CI) and non-critical (NC) patients.
Age range (years)25-3435–4445–5455–6465–7475–84>84
CI vs NCp=0.0030p<0.0001
md = 7
p<0.0001
md = 6
p<0.0001
md = 4
p<0.0001
md = 5
p<0.0001
md = 3
p=0.0006
md = 2
CI vs NC with reported comorbidities*Sample size insufficientp=0.0046
md = 5
p=0.0094
md = 3
p<0.0001
md = 5
p<0.0001
md = 5
p<0.0001
md = 4
p=0.0748
md=2
CI vs NC with comorbidities* reported as ‘none’Sample size insufficientp=0.0011
md = 7
p<0.0001
md = 5
p<0.0001
md = 4
p=0.0305
md = 2
p<0.0001
md = 5
p=0.0339
md = 3
  1. Note: The data is shown per age group for all patients as well as for patients segregated according to the presence or absence of reported comorbidities. ‘md’ refers to the Hodges-Lehmann median difference in prognostic score values between the NC and CI groups in each age category.

    * Patients that were enrolled into the study from the two hospitals that did not report on comorbidities were excluded from the analysis.

  2. † Sample size was too small for analysis in this age group segregated by comorbidities.

    ‡ Patients older than 84 years and with reported comorbidities were the only group where the difference between CI and NC groups was not significant.

Table 6—source data 1

Mann–Whitney test for significance of the difference in prognostic score between critical illness (CI) and non-critical (NC) patients.

https://cdn.elifesciences.org/articles/63195/elife-63195-table6-data1-v2.csv
Table 7
Sysmex XN-1000 haematology analyser parameters used in this study.
Parameter nameStandard parameters*Parameter descriptionMeasurement profile
AS-LYMPHAntibody synthesising lymphocyte count (this is a subset of RE-LYMPH)CBC-DIFF
AS-LYMPH%Antibody-synthesising lymphocyte percentage of total white blood cell countCBC-DIFF
AS-LYMPH%/LAntibody-synthesising lymphocytes as a percentage of lymphocytesCBC-DIFF
BASOYesBasophil countCBC-DIFF
Delta-HeStandard parameter calculated by the equation RET-He minus RBC-HeRET
EOYesEosinophil countCBC-DIFF
HCTYesHaematocritCBC-DIFF
HGBYesHaemoglobin concentrationCBC-DIFF
HYPO-HeThe ratio of the count in the low-level area of the forward scattered light signal in the RBC area of the RET scattergram, to mature red blood cells
(% of hypochromic red blood cells of total red blood cells)
RET
IGImmature granulocyte countCBC-DIFF
IPFImmature platelet fraction (% of immature platelets of total platelet count)RET (PLT-F)
IPF#Immature platelet fraction count (immature platelet absolute count)RET (PLT-F)
LYMPHYesLymphocyte countCBC-DIFF
MCHYesMean corpuscular haemoglobinCBC-DIFF
MCHCYesMean corpuscular haemoglobin concentrationCBC-DIFF
MCVYesMean corpuscular volumeCBC-DIFF
MicroRMicro RBC ratio (proportion of small red blood cells (RBCs) as a % of total RBCs)RET
NEUTYesNeutrophil countCBC-DIFF
MONOYesMonocyte countCBC-DIFF
NEUT-GINeutrophil granularity index (reactivity of neutrophils (cytoplasmic granulation))CBC-DIFF
NEUT-RINeutrophil reactivity index (reactivity of neutrophils (metabolic activity))CBC-DIFF
NRBCNucleated red blood cell countCBC-DIFF
PLTYesPlatelet countCBC-DIFF
RBCYesRed blood cell (erythrocyte) countCBC-DIFF
RBC-HeMature RBC haemoglobin equivalent (optical measurement of red blood cell haemoglobinisation)RET
RE-LYMPHReactive lymphocyte countCBC-DIFF
RE-LYMPH%Reactive lymphocyte percentage of total white blood cell countCBC-DIFF
RE-LYMPH%/LReactive lymphocytes as a percentage of lymphocytesCBC-DIFF
RE-MONONumber of monocytes with a side fluorescent signal > 150 channels representing activated monocytesCBC-DIFF
RE-MONO%/MReactive monocytes as a percentage of monocytesCBC-DIFF
RET#YesReticulocyte countRET
RET-HeReticulocyte haemoglobin equivalent (optical measurement of reticulocyte haemoglobinisation)RET
WBCYesWhite blood cell (leukocyte) countCBC-DIFF
  1. Note: The availability of individual parameters as either diagnostic (IVD) or research use only (RUO) is dependent on regulatory approval status which differs across regions.

    * Standard parameters available in the complete blood count (CBC), differential (DIFF) or reticulocyte measurement (RET) channels across multiple manufacturer haematology analyser platforms.

  2. † Depending on region, the immature platelet count (IPF# and IPF%) are obtained either from the RET or PLT-F channel. PLT-F refers to fluorescent optical platelet measurement.

Additional files

Source data 1

all data file.

https://cdn.elifesciences.org/articles/63195/elife-63195-data1-v2.xlsx
Supplementary file 1

Basic demographic characteristics of COVID-19 PCR confirmed patients enrolled for prognostic score development demographic data by hospital.

https://cdn.elifesciences.org/articles/63195/elife-63195-supp1-v2.docx
Supplementary file 2

Novel parameters of different manufacturers in relation to possible adaptability of the haemocytometric COVID-19 prognostic score.

https://cdn.elifesciences.org/articles/63195/elife-63195-supp2-v2.docx
Transparent reporting form
https://cdn.elifesciences.org/articles/63195/elife-63195-transrepform-v2.pdf
Reporting standard 1

TRIPOD checklist.

https://cdn.elifesciences.org/articles/63195/elife-63195-repstand1-v2.docx

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