Maechler 2020.

Study characteristics
Patient Sampling	Purpose: diagnosis of SARS‐CoV‐2 infection (mild COVID‐19 disease); to describe epidemiological and clinical characteristics; to identify risk factors for SARS‐CoV‐2 infection Design: cross‐sectional cohort study, prospective data collection Recruitment: symptomatic patients presenting at the test site. Subgroups not by testing criteria at that time: (1) high‐risk contacts at a nightclub (26/94 positive). (2) Charité employees 125 asymptomatic. Sample size: n = 4333 (333 cases) Inclusion criteria: until 24 March 2020: symptomatic patients with high‐risk contacts or return from high‐risk area. From 24 March: also symptomatic people with risk factors and if the test capacity allowed also only symptomatic patients. Plus 2 subgroups of high‐risk patients in a nightclub and Charité employees Exclusion criteria: none specified
Patient characteristics and setting	Facility cases: patients with a positive RT‐PCR for SARS‐CoV‐2 infection Facility controls: patients with a negative RT‐PCR for SARS‐CoV‐2 infection Country: Germany Dates: 03 March 2020‐13 April 2020 Symptoms and severity: mild to relatively more severe. Asymptomatic: 12 cases, 431 controls Demographics: age: controls median 34.0 years, cases mean 34.0 years M%/F%: cases 56.8/43.2, controls 48.5/51.5 Exposure history: high‐risk contact: cases 56.8%, controls 36.4%
Index tests	Fever Dyspnoea Chest tightness/pain Chills Fatigue Body aches Cough Rhinorrhoea Diarrhoea Sore throat Headache Anosmia Ageusia
Target condition and reference standard(s)	TC: SARS‐CoV‐2 infection RS: SARS‐CoV‐2 RT‐PCR test (combined oro‐ and nasopharyngeal swab)
Flow and timing	Index tests and reference standard both at presentation
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?	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?	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?	Yes
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