Article Figures & Tables
Tables
Variable No. (%) of admissions* SD† COVID-19
n = 1027Influenza
n = 783Unique patients 972 (94.6) 763 (97.4) N/A Age, yr, median (IQR) 65 (53–79) 68 (55–80) 0.07 Age group, yr 0.09 < 50 218 (21.2) 141 (18.0) 50–75 480 (46.7) 390 (49.8) > 75 329 (32.0) 252 (32.2) Sex, male 607 (59.1) 398 (50.8) 0.17 Charlson score 0.31 0 556 (54.1) 304 (38.8) 1 183 (17.8) 175 (22.3) ≥ 2 288 (28.0) 304 (38.8) Neighbourhood income quintile 0.15 1 (lowest) 351 (34.2) 248 (31.7) 2 177 (17.2) 139 (17.8) 3 153 (14.9) 127 (16.2) 4 163 (15.9) 142 (18.1) 5 (highest) 112 (10.9) 95 (12.1) Missing 71 (6.9) 32 (4.1) Neighbourhood visible minority quintile 0.19 1 (lowest) 100 (9.7) 100 (12.8) 2 196 (19.1) 167 (21.3) 3 264 (25.7) 171 (21.8) 4 181 (17.6) 166 (21.2) 5 (highest) 212 (20.6) 138 (17.6) Missing 74 (7.2) 41 (5.2) Long-term care resident 120 (11.7) 35 (4.5) 0.27 Transfer from acute care hospital 90 (8.8) 24 (3.1) 0.24 Comorbidities‡ Hypertension 356 (34.7) 252 (32.2) 0.05 Diabetes mellitus 284 (27.7) 229 (29.2) 0.04 Renal failure 212 (20.6) 169 (21.6) 0.02 Neurocognitive disorders 174 (16.9) 105 (13.4) 0.10 Coronary heart disease 63 (6.1) 63 (8.0) 0.08 Heart failure 62 (6.0) 98 (12.5) 0.23 COPD 55 (5.4) 96 (12.3) 0.25 Note: COPD = chronic obstructive pulmonary disease, COVID-19 = coronavirus disease 2019, IQR = interquartile range, N/A = not applicable, SD = standardized difference.
↵* Unless indicated otherwise.
↵† SD > 0.1 reflects imbalance between groups. (40)
↵‡ Comorbidities were categorized from ICD-10-CA discharge diagnoses using the Clinical Classification Software Refined tool. (26)
- Table 2:
Presenting vital signs, laboratory values and mortality risk scores in patients with COVID-19 and influenza*
Variable COVID-19 Influenza SD of results‡ SD of no. performed‡ Median (IQR) result† No. (%) performed
n = 1027Median (IQR) result† No. (%) performed
n = 783Temperature, degrees Celsius 36.9 (36.6–37.5) 1000 (97.4) 36.9 (36.6–37.4) 578 (73.8) 0.07 0.71 Systolic BP, mm Hg 126 (114–142) 1019 (99.2) 129 (114–148) 568 (72.5) 0.03 0.83 Diastolic BP, mm Hg 72 (64–82) 1019 (99.2) 73 (65–82) 568 (72.5) < 0.01 0.83 Heart rate, beats per min 88 (76–100) 1019 (99.2) 87 (75–99) 568 (72.5) 0.05 0.83 Respiratory rate, breaths per min 20 (18–22) 1017 (99.0) 18 (18–20) 564 (72.0) 0.18 0.83 S/F ratio 448 (328–462) 1007 (98.1) 452 (438–467) 551 (70.4) 0.40 0.82 Supplemental O2, no. (%)§ 458 (44.9) 1019 (99.2) 212 (37.7) 563 (71.9) 0.15 0.84 Hemoglobin, g/L 127 (111–141) 1006 (98.0) 123 (107–138) 773 (98.7) 0.10 0.06 Hematocrit, L/L 0.38 (0.34–0.42) 1005 (98.9) 0.38 (0.33–0.42) 773 (98.7) 0.06 0.07 White blood cell count, × 109/L 7.6 (5.5–10.6) 1005 (97.9) 7.8 (5.5–10.90) 773 (98.7) < 0.01 0.07 Platelets, × 109/L 214 (164–281) 1002 (97.6) 186 (144–242) 771 (98.7) 0.34 0.07 Neutrophils, × 109/L 5.6 (3.8–8.3) 1002 (97.6) 5.7 (3.9–8.6) 771 (98.7) < 0.01 0.07 Lymphocytes, × 109/L 1.0 (0.7–1.5) 1000 (97.4) 0.9 (0.5–1.3) 771 (98.7) 0.10 0.08 Sodium, mmol/L 137 (133–140) 1002 (97.6) 136 (133–139) 775 (99.0) 0.18 0.11 Bicarbonate, mmol/L 25 (22–27) 939 (91.4) 25 (22–27) 763 (97.4) 0.01 0.27 Creatinine, μmol/L 89 (70–124) 998 (97.2) 96 (72–135) 770 (98.3) 0.07 0.08 Urea, mmol/L 6.6 (4.4–11.7) 417 (40.6) 7.1 (4.6–10.6) 343 (43.8) 0.08 0.07 Albumin, g/L 32 (27–37) 570 (55.5) 33 (29–37) 448 (57.2) 0.15 0.04 Bilirubin, μmol/L 9 (7–13) 850 (82.8) 9 (6–14) 599 (76.5) 0.01 0.16 C-reactive protein, mg/L 77 (30–142) 439 (42.7) 47 (18–100) 59 (7.5) 0.31 0.89 Lactate, mmol/L 1.7 (1.3–2.4) 758 (73.8) 1.7 (1.3–2.5) 605 (77.3) 0.05 0.09 LDH, U/L 315 (222–425) 548 (53.4) 247 (194–364) 152 (19.4) 0.03 0.75 D-dimer, μg/L FEU 1030 (672–1935) 436 (42.5) 911 (433–1780) 41 (5.2) 0.09 0.97 Ferritin, μg/L 463 (210–1124) 390 (38.0) 316 (120–675) 84 (10.7) 0.12 0.67 Glucose, mmol/L 6.7 (5.8–8.8) 921 (89.7) 6.8 (5.70–8.7) 727 (92.8) 0.01 0.11 Arterial Pco2, mm Hg 43 (36–54) 211 (20.5) 42 (34–49) 116 (14.8) 0.21 0.15 Arterial PO2, mm Hg 73 (62–94) 211 (20.5) 81 (66–126) 116 (14.8) 0.36 0.15 Venous Pco2, mm Hg 43 (38–48) 559 (54.4) 44 (38–50) 449 (57.3) 0.13 0.06 Mortality risk score mAPACHE 27 (19–34) N/A 28 (21–35) N/A 0.14 N/A CISSS 0.03 (0.01–0.06) N/A 0.03 (0.02–0.06) N/A 0.05 N/A Lu, category 3, no. (%) 581 (57) N/A 515 (66) N/A 0.19 N/A Hu 0.27 (0.08–0.55) N/A 0.27 (0.10–0.51) N/A 0.05 N/A Xie 0.14 (0.06–0.26) N/A 0.16 (0.07–0.27) N/A 0.04 N/A ISARIC-4C 9 (7–11) N/A 9 (8–11) N/A 0.08 N/A NEWS2 5 (2–9) N/A 4 (1–6) N/A 0.52 N/A Note: BP = blood pressure, CISS = critical illness severity scoring system, COVID-19 = coronavirus disease 2019, FEU = fibrinogen equivalent units (values standardized to this unit across sites if measurement units differed), ISARIC-4C = ISARIC Coronavirus Clinical Characterisation Consortium 4C, IQR = interquartile range, LDH = lactate dehydrogenase, mAPACHE = modified Acute Physiology and Chronic Health Evaluation, N/A = not applicable, NEWS2 = National Early Warning Score, SD = standardized difference, S/F ratio = ratio of oxygen saturation to fraction of inspired oxygen.
↵* We report the first valid laboratory test result and vital sign measurement collected between emergency department (ED) triage and 72 h after admission. Vital signs are not consistently recorded electronically at all hospitals, particularly when patients are in the ED or an intensive care unit. For patients with COVID-19 but not for those with influenza, vital signs were manually abstracted from medical records for the time period between ED triage and 24 h after admission (to calculate mortality risk scores). Mortality risk scores (31)– (36), (39) were calculated based on first valid measurement between ED triage and 24 h after admission, and mean-imputed values when missing (Appendix 1). The possible point ranges for point-based scores were as follows: mAPACHE (0–159), Lu (1–3), ISARIC-4C (0–21), NEWS2 (0–20). The remaining scores are probability based (scores ranging from 0–1). Risk scores presented in this table were calculated based on mean imputation of missing laboratory data. The ISARIC-4C and NEWS2 scores were calculated only for cases with data available regarding mental status (n = 242 admissions with COVID-19 and n = 46 with influenza).
↵† Unless indicated otherwise.
↵‡ SD > 0.1 reflects imbalance between groups.
↵§ Supplemental O2 is the number of patients who required any amount of supplemental oxygen or mechanical ventilation.
- Table 3:
Unadjusted clinical outcomes, resource use and clinical care of patients with COVID-19 and influenza*
Variable No. (%) of admissions† p value COVID-19
n = 1027Influenza
n = 783Death 204 (19.9) 48 (6.1) < 0.001 7-day readmission‡ 32 (4.3) 22 (3.1) 1.0¶ 30-day readmission§ 58 (9.3) 69 (9.6) 0.9 ICU use 271 (26.4) 141 (18.0) < 0.001 Hospital length-of-stay, d, median (IQR) 8.7 (3.6–18.9) 4.8 (2.3–10.4) < 0.001 ICU length-of-stay, d, median (IQR) 10.9 (4.0–17.8) 6.0 (2.3–13.0) < 0.001 ED length-of-stay, h, median (IQR) 8.7 (6.1–13.2) 21.1 (12.0–32.2) < 0.001¶ Invasive mechanical ventilation 190 (18.5) 73 (9.3) < 0.001¶ Gastrointestinal endoscopy 21 (2.0) 27 (3.4) 1.0¶ Bronchoscopy 21 (2.0) 44 (5.6) 0.005¶ Dialysis** 79 (7.7) 43 (5.5) 1.0¶ Thoracic CT 210 (20.4) 168 (21.5) 1.0¶ Respiratory antibiotic†† 730 (71.6) 599 (77.1) 0.6¶ Corticosteroid 170 (16.7) 284 (36.6) < 0.001¶ Warfarin or DOAC 157 (15.4) 156 (20.1) 0.6¶ Note: COVID-19 = coronavirus disease 2019, CT = computed tomography, DOAC = direct-acting oral anticoagulant, ED = emergency department, ICU = intensive care unit, IQR = interquartile range.
↵* Readmission to medical service or medical–surgical intensive care unit at any participating hospital is reported among patients discharged alive and for visits that could be linked to each other with a valid health insurance number. For hospital resources and clinical care, we report the number of patients receiving at least one of the items described.
↵† Unless indicated otherwise.
↵‡ After excluding patients who died and those discharged in the last 7 days of the study period, the denominator was 745 admissions for COVID-19, 720 for influenza.
↵§ After excluding patients who died and those discharged in the last 30 days of the study period, the denominator was 625 admissions for COVID-19, 718 for influenza.
↵¶ p values were adjusted using Bonferroni correction for the 10 secondary outcomes.
↵** Dialysis included hemodialysis and peritoneal dialysis, and included both chronic use and new starts.
↵†† Respiratory antibiotics include all those listed in Appendix 1.
- Table 4:
Clinical outcomes in patients with COVID-19 compared with patients with influenza before and after multivariable adjustment*
Outcome Unadjusted effect† (95% CI) Adjusted effect† (95% CI) Death 3.24 (2.40–4.38) 3.46 (2.56–4.68) ICU use 1.47 (1.22–1.76) 1.50 (1.25–1.80) 30-day readmission 0.97 (0.69–1.35) 0.98 (0.70–1.39) Hospital length-of-stay 1.31 (1.09–1.58) 1.45 (1.25–1.69) ICU length-of-stay 0.93 (0.57–1.52) 1.25 (0.92–1.70) Note: CI = confidence interval, COVID-19 = coronavirus disease 2019, ICU = intensive care unit.
↵* Models were adjusted for patient age, sex, long-term care residence, Charlson comorbidity index score, admitting hospital, neighbourhood income quintile and neighbourhood quintile of proportion of the population who identify as a visible minority. Outcomes reported are: in-hospital death, admission to ICU at any point during hospitalization, readmission to a medical service or medical–surgical ICU at any participating hospital within 30 days of discharge, hospital length-of-stay and ICU length-of-stay.
↵† Poisson regression models were fit for death, ICU, and readmission (effect = relative risk) and negative binomial regression models were fit for hospital and ICU length-of-stay (effect = rate ratio).
- Table 5:
Discriminative performance of mortality prediction scores in patients with COVID-19*
Score Calculation method Predictors No. (%) of admissions with complete data
n = 1027AUC complete data (95% CI) No. (%) of admissions after imputation
n = 1027AUC after imputation (95% CI) Lu Points-based system Age, CRP 390 (37.9) 0.71 (0.66–0.76) 1027 (100) 0.68 (0.65–0.71) Hu Regression-based system Age, CRP, D-dimer, lymphocytes 230 (22.4) 0.78 (0.70–0.86) 1027 (100) 0.72 (0.68–0.76) Xie Regression-based system Age, LDH, lymphocyte, oxygen saturation 469 (45.6) 0.80 (0.75–0.85) 972 (94.6) 0.75 (0.71–0.79) ISARIC-4C Points-based system Age, sex, Charlson comorbidities, respiratory rate, oxygen saturation, GCS score, urea, CRP 12 (1.2) N/A† 242 (23.6) 0.78 (0.70–0.85) mAPACHE Points-based system Age, mechanical ventilation, hematocrit, WBC, sodium, glucose, bilirubin, urea, creatinine, temperature, heart rate, respiratory rate, mean arterial blood pressure, metastatic cancer, AIDS, hepatic failure, cirrhosis, leukemia, lymphoma, immunosuppression, multiple myeloma 348 (33.9) 0.86 (0.83–0.90) 976 (95.0) 0.81 (0.78–0.85) CISSS Regression-based system Age, mechanical ventilation, surgery, hematocrit, WBC, sodium, glucose, bilirubin, creatinine, bicarbonate, albumin, temperature, heart rate, respiratory rate, mean arterial blood pressure, metastatic cancer, AIDS, hepatic failure, cirrhosis, leukemia, lymphoma, immunosuppression, multiple myeloma 357 (34.8) 0.83 (0.78–0.88) 976 (95.0) 0.80 (0.77–0.84) NEWS2 Points-based system Respiratory rate, oxygen saturation, systolic blood pressure, heart rate, level of consciousness/new confusion, temperature 242 (23.6) 0.72 (0.63–0.80) 242 (23.6) 0.72 (0.63–0.80) Note: AUC = area under the receiver operating characteristic curve, CI = confidence interval, CISS = critical illness severity scoring system, COVID-19 = coronavirus disease 2019, CRP = C-reactive protein, GCS = Glasgow Coma Scale, ISARIC-4C = ISARIC Coronavirus Clinical Characterisation Consortium 4C, mAPACHE = modified Acute Physiology and Chronic Health Evaluation, N/A = not applicable, NEWS2 = National Early Warning Score, WBC = white blood cell count.
↵* Mortality risk scores (31)– (36), (39) were calculated based on first valid measurement between emergency department triage and 24 hours after admission. We report model performance based on hospitalizations with complete data for all inputs and after mean imputation of missing laboratory test results (see Appendix 1 for details). We did not impute missing vital signs or mental/neurologic status data because we did not think it was reasonable to assume these values would be normal. The mortality rate in the 242 hospitalizations on which ISARIC-4C and NEWS2 scores were validated was 17.4% (42 deaths).
↵† Insufficient sample to calculate.