Chew 2021.

Study characteristics
Patient Sampling	Purpose: diagnosis of SARS‐CoV‐2 infection (mild COVID‐19 disease); to develop a prediction model to identify patients who are at low risk of having COVID‐19 Design: cross‐sectional cohort study, retrospective data collection Recruitment: all patients admitted to the Pneumonia and Acute Respiratory Infection (PARI) wards of Changi General Hospital Sample size: n = 1228 (52 cases) Inclusion criteria: all patients admitted to PARI wards Exclusion criteria: none specified, for patients with multiple admissions during the study period, analysis was limited to the first PARI admission
Patient characteristics and setting	Facility cases: RT‐PCR‐positive for SARS‐CoV‐2 Facility controls: RT‐PCR‐negative for SARS‐CoV‐2 Country: Singapore Dates: 10 February 2020‐30 April 2020 Symptoms and severity: not specified, mild to moderate severity Demographics: median age cases 48 years, controls 64 years M%/F%: total cohort 59.9/40.1 Exposure history: contact with people with acute respiratory infection, cases 36%, controls 4%; travel history: cases 3%, controls 2%
Index tests	Fever Cough Sore throat Rhinorrhoea Anosmia Breathlessness Headache Chest discomfort
Target condition and reference standard(s)	TC: SARS‐CoV‐2 infection RS: RT‐PCR for SARS‐CoV‐2 (nasopharyngeal and oropharyngeal swab)
Flow and timing	Timing not specified
Comparative
Notes	Funding: none declared
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Yes
Was a case‐control design avoided?	Yes
Did the study avoid inappropriate exclusions?	Yes
Did the study avoid inappropriate inclusions?	Yes
Could the selection of patients have introduced bias?		Low risk
Are there concerns that the included patients and setting do not match the review question?			Low concern
DOMAIN 2: Index Test (All tests)
Were the index test results interpreted without knowledge of the results of the reference standard?	Unclear
If a threshold was used, was it pre‐specified?	No
Could the conduct or interpretation of the index test have introduced bias?		High risk
Are there concerns that the index test, its conduct, or interpretation differ from the review question?			Low concern
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Yes
Were the reference standard results interpreted without knowledge of the results of the index tests?	Unclear
Could the reference standard, its conduct, or its interpretation have introduced bias?		Low risk
Are there concerns that the target condition as defined by the reference standard does not match the question?			Low concern
DOMAIN 4: Flow and Timing
Was there an appropriate interval between index test and reference standard?	Unclear
Did all patients receive the same reference standard?	Yes
Were all patients included in the analysis?	Yes
Could the patient flow have introduced bias?		Unclear risk