Liu 2020c.

Study characteristics
Patient Sampling	Purpose: To diagnose Covid‐19 acute phase infection and convalescent‐phase infection Design: Two‐group study to estimate sensitivity and specificity [1] Test group ‐ Confirmed COVID patients, serum from hospitalised patients (n = 206) [2] Control group (n = 270) – Non‐Covid pre‐pandemic healthy donors Recruitment: [1] Test samples ‐ Confirmed Covid patients, samples were collected from patients who were treated in the General Hospital of the Central Theatre Command of the People’s Liberation Army (PLA) between January 18 and April 4, 2020 [2] Control group (n = 270) – randomly collected from healthy blood donors who donated blood in May 2019, in Wuhan, China Prospective or retrospective: Both [1] Test samples – prospective [2] Pre‐pandemic healthy donors ‐ retrospective Sample size: 476 (206) Further detail: Inclusion: [1] Subjects who had positive RT‐PCR on pharyngeal swab specimens and were treated at the General Hospital of the Central Theatre Command of the People’s Liberation Army (PLA) between January 18 and April 4, 2020 [2] Healthy blood donors who donated blood in May 2019, in Wuhan, China. The healthy blood donors were healthy people without other infection and auto‐immune diseases. Exclusion: [1] Test group ‐ PCR‐negative samples [2] Those with other infections and auto‐immune diseases
Patient characteristics and setting	Setting: Hospital inpatients Location: General Hospital of the Central Theatre Command of the People’s Liberation Army (PLA), Wuhan, Hubei Country: China Dates: [1] between January 18 and April 4, 2020 Symptoms and severity: 54 patients were critical cases, 152 patients were non‐critical cases. Demographics: [1] Among the patients, 126 (61.1 %) were males, and 80 (38.8 %) were females. The median age of these patients was 57 years (IQR, 43–68 years), ranging from 17 to 91 years. Exposure history: Not stated (possibly all from Wuhan area) Non‐Covid group 1: [2] Healthy blood donors Source: They donated blood in May 2019, in Wuhan, China. Characteristics: The healthy blood donors were healthy people without other infection and auto‐immune diseases. The demographics (including age and gender) of patients and healthy donors were compared, with no significant differences. Non‐Covid group 2: NA Source: NA Characteristics: NA
Index tests	Test name: Chemiluminescence Microparticle Immunoassays (CMIA). Test names not stated [A] IgM‐CMIA [B] Ab‐CMIA Manufacturer: [A] and [B] Xiamen InnoDx Biotech Co., Ltd., China (Xiamen, China) Antibody: [A] IgM [B] Ab (total antibodies) Antigen target: [A] and [B] RBD (receptor binding domain) of the SARS‐CoV‐2 spike‐protein, S‐protein of SARS‐CoV‐2 Evaluation setting: [A] and [B] Laboratory Test method: [A] chemiluminescence microparticle immunoassays (μ‐chain capture immunoassay) [B] chemiluminescence microparticle immunoassay (double‐antigens sandwich immunoassay) Timing of samples: Symptom onset 0‐7 days pso: 26/206 8‐14 days pso: 70/206 15‐21 days pso: 72/206 > 21 days pso: 38/206 Samples used: [1] Serum [2] Serum Test operator: Lab personnel from hospital laboratories Definition of test positivity: [A] and [B]: A test was determined as positive if the signal/cut‐off (S/CO) ratio ＞ 1.0. Blinding reported: Not stated Threshold predefined: yes (the cut‐off value of IgM and total antibodies were calculated according to the manufacturer’s instructions)
Target condition and reference standard(s)	Reference standard: RT‐PCR nucleic acid testing kit (Daan, Guangzhou, China) Samples used: [1] pharyngeal swab specimens Timing of reference standard: [1] During patient care, timing not stated Blinded to index test: yes, performed prior to index test Incorporated index test: No Definition of non‐COVID cases: [2] Untested, pre‐pandemic healthy blood donors who donated blood in May 2019 Samples used: [2] Untested, pre‐pandemic Timing of reference standard: [2] Untested, pre‐pandemic Blinded to index test: Yes, prior to index test Incorporated index test: No
Flow and timing	Time interval between index and reference tests: Not stated All patients received same reference standard: No ([1] PCR, [2] Pre‐pandemic samples) Missing data: Not stated Uninterpretable results: Not stated Indeterminate results: Not mentioned (possibly none as test has no borderline range) Unit of analysis: Patients
Comparative
Notes	Funding: We thank Xiamen InnoDx Biotech Co., Ltd., China for providing assistance in CMIA detection. This work was supported by the National Natural Science Foundation of China (81801984), the China Postdoctoral Science Foundation (2019M664008), and the Wuhan Young and Middle‐aged Medical Backbone Talents Training Project (Wuweitong [2019] 87th). Publication status: Published paper Source: Journal of Clinical Virology Elsevier Author COI: The authors declared that no conflict of interest existed.
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?	No
Were all patients included in the analysis?	Yes
Did all participants receive a reference standard?	Unclear
Were results presented per patient?	Yes
Could the patient flow have introduced bias?		High risk