Sun 2020a Study characteristics Patient Sampling Purpose: algorithm development for estimating risk COVID‐19Design: cross‐sectional, retrospective studyRecruitment: patients presenting at the designated national outbreak screening centre and tertiary care hospital in Singapore for SARS‐CoV‐2 testing. Patients were either self‐referred, referred from primary care facilities, or were at‐risk cases identified by national contact tracing efforts (recruited n = 991)Sample size: n = 788 (n = 54)Inclusion criteria: patients presenting to the centre:self‐referred referred from primary care facilities at‐risk cases identified by national contact tracing efforts Exclusion criteria: PCR results not available at time of data collection ‐ no electronic medical records ‐ unavailable vital sign records Patient characteristics and setting Facility cases: positive SARS‐CoV2 RT‐PCR testFacility controls: all SARS‐CoV‐2 RT‐PCR results were negative (minimum 2 test negatives in high‐risk patients, minimum 1 test low‐risk patients)Country: SingaporeDates: 26 January 2020‐16 February 2020Symptoms and severity: 252 (33.2%) symptoms > 5 days at presentation, 75 (9.5%) any comorbiditybody temperature heart rate respiratory rate systolic BP diastolic BP cough sputum production shortness of breath rhinnorhoea or nasal congestion sore throat auscultation finding of pneumonia other respiratory symptoms gastrointestinal symptoms Demographics: median age 34 years (range 7 years‐98 years, IQR 27‐45) (cases median 42 years, range 16‐79; controls 34 years (range 7‐98); M/F: 48.3%/51.7% F (cases M: 88 (88.9%))Exposure history: contact with a known COVID‐19 case (20.1% (32/54 cases (59.3%)); 126/734 controls (17.2%), contact with travellers from China (22.1%, 15/54 cases (27.8%); 42/734 controls (5.7%)), recent travel history, and visit to hospital in China within 14 days prior to symptom onset (0.8%) Index tests Body temperature Heart rate Respiratory rate Systolic BP Diastolic BP Cough Sputum production Shortness of breath Rhinnorhea or nasal congestion Sore throat Auscultation finding of pneumonia Other respiratory symptoms GI symptoms Target condition and reference standard(s) TC: SARS‐CoV‐2 infection RS: SARS‐CoV‐2 2 commercial assays 2‐target (1 assay: Orf1ab and N ‐ other unclear) RT‐PCR Flow and timing Time interval not specified Comparative   Notes   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? No     Did the study avoid inappropriate exclusions? Yes     Did the study avoid inappropriate inclusions? Yes     Could the selection of patients have introduced bias?   High risk   Are there concerns that the included patients and setting do not match the review question?     High DOMAIN 2: Index Test (All tests) Were the index test results interpreted without knowledge of the results of the reference standard? Yes     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? No     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?   Low risk