Xiao 2020a.

Study characteristics
Patient Sampling	Purpose: Single‐group study to estimate sensitivity for diagnosing active or prior infection Design: Confirmed cases of COVID‐19 (n = 34) according to the diagnosis and treatment guideline for SARS‐CoV‐2 from Chinese National Health Committee (Version 5) and the interim guidance from Centers for Disease Control and Prevention Recruitment method: not reported Sample size: 34 (34)
Patient characteristics and setting	Setting: Inpatients Location: Tongji Hospital, Wuhan Country: China Dates: 1‐29 February 2020; final follow‐up date 3 March 2020 Exposure history: NR Patient characteristics: 12 female, 22 male. Median age (review team estimated) 49 years (range 26‐87), 22 (65%) male
Index tests	Test name: Manufacturer: Shenzhen Yahuilong Biotechnology Co. Ltd. Antibody: IgM and IgG Antigen target: Not described Evaluation setting: laboratory test Test method: CLIA Timing of samples: Samples acquired ≥ 2 weeks after symptoms onset for 32/34 participants; and on day 2 and day 3 for remaining 2 participants Samples used: Plasma Test operator: not reported Definition of test positivity: not reported
Target condition and reference standard(s)	Reference standard: COVID‐19 according to diagnosis and treatment guideline for SARS‐CoV‐2 from Chinese National Health Committee (Version 5) Timing of reference standard: not described Blinded to index test: Not described Incorporated index test:
Flow and timing	Time interval between index and reference standard: Not described Timing: Not stated Missing data: None Uninterpretable results: None Indeterminate results: None
Comparative
Notes	Funding: No funding sources declared Author COI: No conflicts of interest declared Source: Pre‐proof paper accepted for publication (Journal of Infection)
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?	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 (All tests)
DOMAIN 2: Index Test (Antibody 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?	Unclear
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?			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
The reference standard does not incorporate the index test	Yes
Could the reference standard, its conduct, or its interpretation have introduced bias?		Unclear 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?	Unclear
Were all patients included in the analysis?	Unclear
Did all participants receive a reference standard?	Yes
Were results presented per patient?	Yes
Could the patient flow have introduced bias?		Unclear risk