Table 2

Model parameters

StudyModel constructionFeaturesPredicted outcomeData processing
Gong et al5Nomogram built from LASSO algorithm and logistic regression modelAge, direct bilirubin, BUN, CRP, LDH, albumin, RDWShortness of breath, respiratory rate ≥30/min, SpO2 ≤93% or PaO2/FiO2 ≤300 mm HgVariables with >7% values missing excluded. Other missing variables imputed by expectation maximisation
Zhou et al8Formula derived from logistic regressionNeutrophil count, lymphocyte count, D-dimerRespiratory rate ≥30/min, severe respiratory distress, SpO2 <90% on room air, ARDS, sepsis or septic shockNot discussed
Zou et al9Nomogram derived from logistic regression and Cox regression modelAge, disturbance of consciousness (GCS under 15,), LDH, CRP, chronic heart disease, chronic renal insufficiency, septic shockIn-hospital mortalityNot discussed
Xie et al5Nomogram derived from logistic regressionAge, LDH, log (lymphocyte count), SpO2In-hospital mortalityNot discussed
Yan et al6Multitree XGBoostLDH, lymphocyte percent, CRPIn-hospital mortalityPregnant, lactating women, minors, cases with data <80% complete excluded. Missing data ‘−1’ padded
Levy et al10LASSO regression, multivariate logistic regressionAge, BUN, Emergency Severity Index, RDW, neutrophil count, serum bicarbonate, serum glucoseIn-hospital mortalityNot discussed
Zhang et al11Logistic regressionAge, sex, neutrophil count, lymphocyte count, platelet count, CRP, D-dimer, creatinine, ALTTask 1: ARDS, intubation, ECMO, ICU admission or in-hospital mortalityNot discussed
Task 2: ARDS, intubation, ECMO, ICU admission or in-hospital mortality
Guo et al12Cox regressionAge, underlying chronic disease, neutrophil-to-lymphocyte ratio, CRP, D-dimerShortness of breath, respiratory rate ≥30/min, SpO2 ≤93%, PaO2/FiO2 ≤300 mm Hg, respiratory failure with mechanical ventilation, circulatory shock, multiple organ or failure with ICU admissionCases with missing data excluded
Hu et al13Logistic regressionAge, CRP, lymphocyte count, D-dimerIn-hospital mortalityMissing values imputed using bagging trees
Carr et al14Logistic regression augmented by XGBoostNEWS2 (respiratory rate, SpO2, systolic BP, heart rate, GCS<15, temperature, supplemental oxygen (binary)), CRP, neutrophil count, eGFR, albumin, ageIn-hospital mortality or ICU admissionNot discussed
  • ALT, alanine aminotransferase; ARDS, acute respiratory distress syndrome; BP, blood pressure; BUN, blood urea nitrogen; CRP, C-reactive protein; ECMO, extracorporeal membrane oxygenation; eGFR, estimated glomerular filtration rate; FiO2, fraction of inspired oxygen; GCS, Glascow coma score; ICU, intensive care unit; LASSO, least absolute shrinkage and selection operator; LDH, lactate dehydrogenase; NEWS2, national early warning score 2; PaO2, partial pressure of oxygen; RDW, erythrocyte distribution width; SpO2, oxygen saturation.