Romero‐Gameros 2021.

Study characteristics
Patient Sampling	Purpose: diagnosis of SARS‐CoV‐2 infection (mild COVID‐19 disease); to evaluate and establish the diagnostic performance of symptoms and signs in patients with suspected COVID‐19 Design: cross‐sectional cohort study, prospective data collection Recruitment: patients who came to the ED for suspected COVID‐19. Patients were selected through a non probabilistic sampling of consecutive cases according to the order of arrival at the ED Sample size: n = 2137 (1148 cases) Inclusion criteria: > 17 years, high clinical probability of SARS‐CoV‐2, confirmatory RT‐PCR available Exclusion criteria: no RT‐PCR test done
Patient characteristics and setting	Facility cases: positive RT‐PCR test for SARS‐CoV‐2 Facility controls: negative RT‐PCR test for SARS‐CoV‐2 Country: Mexico Dates: 14 April 2020‐21 July 2020 Symptoms and severity: mild to moderate severity, high prevalence (> 50%) of symptoms such as cough, asthenia, myalgia and headache; oxygen saturation < 93% in 11% of cases and 4% of controls Demographics: age: controls mean 42.8 years, cases mean 48.6 years M%/F%: cases 55.7/44.2, controls 46.8/53.1 Exposure history: not specified
Index tests	Fever (> 38 °C) Cough Odynophagia Thoracic pain Aesthenia Myalgia Rhinorrhoea Headache Anosmia Conjunctivitis Dyspnoea Temperature Heart rate Respiratory rate Systolic BP Diastolic BP Oxygen saturation (median) Oxygen saturation < 93%
Target condition and reference standard(s)	TC: SARS‐CoV‐2 infection RS: RT‐PCR (nasopharyngeal swabs)
Flow and timing	Timing not specified
Comparative
Notes	Funding: supported by the Mexican Institute of Social Security
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?	Unclear
Did the study avoid inappropriate inclusions?	No
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?			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?	Yes
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