Beck 2021.

Study characteristics
Patient Sampling	Single‐group study estimating sensitivity and specificity: all patients with signs and symptoms of COVID‐19 presenting to an urgent care centre (n = 347) Recruitment: consecutive ("all patients") Prospective or retrospective: not stated; appears prospective Sample size (cases): 347 (61)
Patient characteristics and setting	Setting: urgent care centre Location: Advocate Aurora Health Urgent Care Center, West Bend, WI Country: USA Dates: not stated Symptoms and severity: all symptomatic; no further details Demographics: age range 1‐90 years; ≤ 18 years 35.4%, 19‐50 years 38.3%, > 50 years 26.2% of participants Exposure history: not reported
Index tests	Test name: SOFIA SARS Antigen FIA Manufacturer: Quidel Antibody: SARS‐CoV Ag target: not reported Test method: FIA Samples used: nasal; collection not described but appears to be HCW ("providers" mentioned in acknowledgements). IFU describes NMT samples Transport media: none; "swabs were carefully returned to the paper envelope in which they came and were placed in a sealed plastic specimen transport bag" Sample storage: none; "specimens were delivered to the laboratory (located within the same building) within 10 minutes of collection" Test operator: lab staff Definition of test positivity: not stated; "tested … according to the manufacturer’s package insert" Blinding reported: yes; done first and in separate lab Timing of samples: ≤ 5 days pso 298, 86.1%; > 5 days pso 48, 13.9%
Target condition and reference standard(s)	Reference standard: transcription‐mediated amplification (TMA); Hologic Aptima Panther SARS‐CoV‐2 TMA test. Cepheid Xpert Xpress SARS‐CoV‐2 RT‐PCR used for discrepant samples (after approx. 3 weeks' frozen storage) Definition of non‐COVID cases: as for cases Genetic target(s): not stated Samples used: NP in Amies bacterial transport medium (Copan, Brescia, Italy) Timing of reference standard: as for index test Blinded to index test: not stated; specimens were refrigerated and sent via courier to the central laboratory of ACL Laboratories Incorporated index test: no
Flow and timing	Time interval between index and reference tests: simultaneous; paired swabs, NP collected first All participants received same reference standard: yes Missing data: 1 sample only (low risk) Uninterpretable results: 1 sample invalid on SOFIA Indeterminate results (index test): none reported Indeterminate results (reference standard): none reported. Discrepant analysis: 2/14 FNs were negative on Xpert Xpress; 1/1 FPs also negative Xpert Xpress Unit of analysis: participant
Comparative
Notes	Funding: none reported Publication status: published Source: Journal of Clinical Microbiology Author COI: none reported
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 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 (Evaluations of single test application)
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?	Yes
Could the conduct or interpretation of the index test have introduced bias?		Low risk
Are there concerns that the index test, its conduct, or interpretation differ from the review question?			Low concern
DOMAIN 2: Index Test (Evaluations of serial (repeat) testing)
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	No
Were the reference standard results interpreted without knowledge of the results of the index tests?	Unclear
Reference standard does not incorporate result of index test?	Yes
Could the reference standard, its conduct, or its interpretation have introduced bias?		High risk
Are there concerns that the target condition as defined by the reference standard does not match the question?			High
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?	No
Did all participants receive a reference standard?	Yes
Could the patient flow have introduced bias?		Low risk