Zimmerman 2020.

Study characteristics
Patient Sampling	Purpose: diagnosis of SARS‐CoV‐2 infection (mild COVID‐19 disease); to develop a data‐driven set of clinical indicators for COVID‐19 that would help to identify outpatient symptoms and those who most benefit from limited testing availability Design: cross‐sectional cohort study, prospective data collection Recruitment: symptomatic individuals who had either exposure to a case of COVID‐19 or a typical respiratory illness symptom were scheduled at a centralised outpatient COVID‐19 testing facility Sample size: n = 736 (55 cases) Inclusion criteria: either exposure to a case of COVID‐19 or a typical respiratory illness symptom Exclusion criteria: asymptomatic individuals
Patient characteristics and setting	Facility cases: adult patients testing positive for SARS‐CoV‐2 infection Facility controls: adult patients testing negative for SARS‐CoV‐2 infection Country: Pennsylvania, USA Dates: 29 March 2020‐26 April 2020 Symptoms and severity: mild to moderate severity Demographics: not specified Exposure history: contact with COVID‐19 case: cases: 70%, controls: 21%
Index tests	Fever Chills Cough Sore throat Shortness of breath Muscle aches Abdominal pain Nausea/vomiting Diarrhoea Headache Decrease or loss of taste or smell
Target condition and reference standard(s)	TC: SARS‐CoV‐2 infection RS: PCR for SARS‐CoV‐2 (specimen not specified)
Flow and timing	Not specified
Comparative
Notes	Funding: supported through a co‐operative agreement with the Centers for Disease Control and Prevention (CDC) through grant number U01 IP000467 and the National Institutes of Health grant number 1UL1 TR001857. The US Flu VE Network is supported through co‐operative agreements funded by CDC.
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Unclear
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?		Unclear risk
Are there concerns that the included patients and setting do not match the review question?			Unclear
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?	Unclear
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