Study characteristics
Patient Sampling  Purpose: to analyse OTDs as a diagnostic criterion for COVID‐19Design: cross‐sectional, prospective single‐centre studyRecruitment: all suspected cases presenting to the EDSample size: n = 870 (cases = 154)Inclusion criteria:presence of respiratory symptoms and suspicious epidemiological links or travel history or
new onset OTD
Exclusion criteria: not specified
Patient characteristics and setting  Facility cases: positive RT‐PCR for 2019‐nCovFacility controls: negative RT‐PCR for 2019‐nCovCountry: SingaporeDates: 26 March 2020‐10 April 2020Symptoms and severity: loss of sense of smell/tasteDemographics: not specifiedExposure history: close contact of a confirmed COVID‐19 case: cases 42/112, controls 37/679
Index tests  Loss of sense of smell/taste
Target condition and reference standard(s)  TC: SARS‐Cov‐2 infection
RS: RT‐PCR (oropharyngeal swabs)
Flow and timing  Time interval: same day
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?  Unclear      
Was a case‐control design avoided?  Yes      
Did the study avoid inappropriate exclusions?  Unclear      
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