Schildgen 2020 [A].

Study characteristics
Patient Sampling	Unclear design; appears to be single cohort with deliberate sampling of PCR+/PCR‐: [1] RT‐PCR positive BAL or throat wash samples (n=42) [2] RT‐PCR negative samples (n=31) Described as pilot sample panel Recruitment: Appears to be convenience Prospective or retrospective: Not stated; presume retrospective
Patient characteristics and setting	Setting: Not stated Location: Authors institution: Kliniken der Stadt Köln gGmbH (Koln city clinics) Country: Germany Dates: Not stated Symptoms and severity: Not stated for BAL samples, throat wash from 23 symptomatic and 27 asymptomatic people. Demographics: Not stated Exposure history: Not stated
Index tests	Comparative study of three Ag tests (no product codes reported); Schildgen 2020 [A] data relate to test [A], see Schildgen 2020 [B] and Schildgen 2020 [C] for data relate to tests [B] and [C]. Test name: [A] BIOCREDIT [B] Panbio [C] SARS‐CoV‐2 Rapid Antigen test Manufacturer: [A] RapiGEN [B] Abbott [C] Roche Antibody: Not stated Antigen target: Not stated Test method: All LFA Samples used: BAL (n=13); throat wash (n=50, including 27 from asymptomatic) Transport media: Not stated Sample storage: Not stated Test operator: Not stated; presume lab staff Definition of test positivity: As per manufacturer Blinding reported: Not stated Timing of samples: Not stated
Target condition and reference standard(s)	Reference standard: RT‐PCR; RealStar® SARS‐CoV‐2 RT‐PCR Kit, Altona, Germany Definition of non‐COVID cases: As for cases Genetic target(s): Not stated Samples used: BAL or throat wash; As per index test Timing of reference standard: Not stated Blinded to index test: Not stated Incorporated index test: No
Flow and timing	Time interval between index and reference tests: Same swab All patients received same reference standard: Yes Missing data: 8 PCR invalid samples also tested; 2/8 invalid in one AG assay each, 3/8 negative in all 3 Ag assays Uninterpretable results: None reported Indeterminate results (index test): None reported Indeterminate results (reference standard): None reported Unit of analysis: Unclear
Comparative
Notes	Funding: The study did not receive any external funding Publication status: preprint Source: medRxiv Author COI: The authors declare that they have no conflicts of interest
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	No
Was a case‐control design avoided?	No
Did the study avoid inappropriate exclusions?	Unclear
Did the study avoid inappropriate inclusions?	Unclear
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?			High
DOMAIN 2: Index Test (Antigen tests)
Were the index test results interpreted without knowledge of the results of the reference standard?	Unclear
If a threshold was used, was it pre‐specified?	Yes
Could the conduct or interpretation of the index test have introduced bias?		Unclear risk
Are there concerns that the index test, its conduct, or interpretation differ from the review question?			High
DOMAIN 2: Index Test (Rapid molecular tests)
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
Were results presented per patient?	Unclear
Could the patient flow have introduced bias?		High risk