Shen 2020b.

Study characteristics
Patient Sampling	Purpose: To investigate the utility of the IgM‐based gold immunochromatographic assay as a candidate clinical diagnostics assay in COVID‐19 patients Multi‐group study to estimate sensitivity and specificity for the diagnosis of active disease/identification of previous disease [1] COVID‐19 patients (n = 58) in time‐based analysis [2] COVID‐19 patients (n = 70, incl 45 PCR‐positive); acute phase only (4‐14 days pso); not eligible for inclusion [3] patients with non‐coronaviral respiratory illness (n = 10) (2 confirmed for influenza A virus, 3 confirmed for influenza B virus, 3 confirmed for respiratory syncytial virus and 2 confirmed for adenovirus) [4] negative control, consisted of 50 sera samples collected from 50 healthy people assessed by physical examination (n = 50) Recruitment: patients at the Xiangyang Central Hospital ‐ no further information Prospective or retrospective: unclear. Sample size: 118 (58) patients eligible for inclusion Further detail: Not stated
Patient characteristics and setting	Setting: patients at the Xiangyang Central Hospital ‐ appeared to be mixed settings Location: Xiangyang Central Hospital, Affiliated Hospital of Hubei University of Arts and Science, Xiangyang Hubei Province 441021, People’s Republic of China Country: China Dates: Not stated Symptoms and severity: mild (n = 50) and severe (n = 8) Demographics: Age: Median (IQR) 52 (36–61); range 8‐81 years; 55% (32/58) female Exposure history: Not stated
Index tests	Test name: SARS‐CoV‐2 IgM GICA kit Manufacturer: Shanghai Outdo Biotech Co., China Antibody: IgM Antigen target: immobilised SARS‐CoV‐2 antigen (N and S recombinant proteins forming an antibody–antigen complex) Evaluation setting: POC, performed in laboratory Test method: colloidal gold immunochromatographic assay (GICA) Timing of samples: 0 to 31 days after symptom onset < 4 days pso: 41/155 (26.5%) 4‐7 days pso: 31/155 (20.0%) 8‐14 days pso: 48/155 (31.0%) 15‐21 days pso: 23/155 (14.8%) > 21 days pso: 12/155 (7.7%) Samples used: Serum Test operator: Not stated Definition of test positivity: The serum was considered positive if bands could be visualised on both the test and control lines. Each sample was repeated in triplicate. Blinding reported: Unclear Threshold predefined: As per manufacturer's instructions
Target condition and reference standard(s)	Reference standard: RT‐PCR Samples used: Not stated Timing of reference standard: Not stated Blinded to index test: Yes, prior to index test Incorporated index test: No Definition of non‐COVID cases: NA
Flow and timing	Time interval between index and reference tests: Not stated All patients received same reference standard: Yes Missing data: Not stated Uninterpretable results: Not stated Indeterminate results: Not stated Unit of analysis: Samples
Comparative
Notes	Funding: This work was supported by the Doctoral Fund of Xiangyang Central Hospital (RC202001), the One Belt and One Road major project for infectious diseases (2018ZX10101004‐ 003). Gary Wong is supported by a G4 grant from IP, FMX and CAS. Publication status: Published paper Source: Emerging Microbes & Infections Author COI: No potential conflict 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?	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?	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?			Unclear
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
The reference standard does not incorporate the index test	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?			High
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
Did all participants receive a reference standard?	Unclear
Were results presented per patient?	No
Could the patient flow have introduced bias?		High risk