Table 1

Comparison of participant characteristics in the derivation and external validation cohorts

CharacteristicDerivation cohort
(N=4035)
External validation cohort
(N=2202)
P value
Missing valuesValid casesValueMissing valuesValid casesValue
Demographics
 Median age (IQR)—years4403170 (56–80)0220261 (46–78)<0.001
 Male sex—N (%)4839872433 (61.0)122011054 (47.9))<0.001
Comorbidity
 Current smoker—N (%)1.1182917197 (6.8)972105156 (7.4)<0.001
 Hypertension—N (%)2540102052 (51.2)172185907 (41.5)<0.001
 Diabetes—N (%)334002871 (21.8)162186378 (17.3)<0.001
 Chronic kidney disease—N (%)354000199 (5.0)203916376 (46.6)<0.001
 Obesity (BMI>30)—N (%)4293606497 (13.8)612141233 (10.9)0.001
 Chronic inflammatory disease—N (%)383997231 (5.8)02202255 (11.6)<0.001
 HIV/AIDS—N (%)73396226 (0.7)20218213 (0.6)<0.001
Disease chronology
 Δt onset of symptoms to admission, days—median (IQR)46235735 (2–7)93912638 (5–11)<0.001
Symptoms and signs<0.001
 History of fever—N (%)3540003240 (81.0)3521671568 (72.4)<0.001
 Cough—N (%)5139842862 (71.8)3621661098 (50.7)<0.001
 Malaise—N (%)12139142505 (64.0)382164907 (41.9)<0.001
 Dyspnoea—N (%)5539801953 (49.1)3721651098 (50.7)<0.001
 Myalgia/Arthralgia—N (%)2263809947 (24,9)2160588 (27.2)0.045
 Sputum production—N (%)723963956 (24.1)612141311 (14.5)<0.001
 Vomiting/Nausea—N (%)1113924488 (12.4)02202295 (13.4)<0.001
 Diarrhoea—N (%)1233912471 (12.0)372165482 (22.3)<0.001
Radiology
 Lung infiltrates on admission—N (%)16538703002 (77.6)821941559 (71,1)<0.001
Oxygenation
 Age adjusted low SaO2—N (%)4903545942 (26.6)4231779344 (19.3)<0.001
Laboratory parameter
 Neutrophil-to-lymphocyte ratio—Median (IQR)9039454.5 (2.7–7.7)63615664.7 (2.9–8.0)0.013
 Platelets—number×1012 L—Median (IQR)753960178 (139–226)6361566218 (169–285)<0.001
 D-dimer—ng/mL—Median (IQR)24721563580 (339–1040)1325877736 (418–1374)<0.001
 eGFR—mL/min/1.73 m2 (CKD-EPI)—Median (IQR)140389578.4 (56.5–93.6)645155788.9 (71.5–103.1)<0.001
 ALT—U/L—Median (IQR)796323926 (18–41)719148331 (20–48)<0.001
 Serum albumin—g/dL—Median (IQR)262414113.5 (3.2–3.9)107111314.3 (3.9–4.5)<0.001
 Lactate dehydrogenase—U/L—Median (IQR)14572578290 (224–403)9671235320 (254–404)<0.001
 C reactive protein—mg/L—Median (IQR)358367754 (20–116)782142075 (25–151)<0.001
  • ALT, alanine aminotransferase; BMI, body mass index; eGFR, estimated glomerular filtration rate; SaO2, saturation of oxygen; Δt, time interval.