Hu 2020b [A].

Study characteristics
Patient Sampling	Purpose: Diagnosis of acute and convalescent‐phase Covid‐19 infection Design: Single or multi‐group study estimating sensitivity and specificity (design unclear), including: participants who visited Huangshi Central Hospital during specified time period, described as [1] PCR‐positive COVID‐19 group (n = 68) [2] Suspected Covid group (PCR‐negative but with fever and other respiratory symptoms) (n = 9) [3] Group with other diseases and negative PCR (n = 101) Study authors considered group [2] and [3] as disease‐negative. Recruitment: Unclear Prospective or retrospective: Unclear; presumed retrospective given time period from early in the pandemic Sample size: 178 (68) Further detail: No more details available
Patient characteristics and setting	Setting: Unclear; no details Location: Huangshi Central Hospital, Hubei Province Country: China Dates: January and February 2020 Symptoms and severity: Unclear Demographics: Age: range 30 years to 90 years; no mean available Sex: 36/68 (53%) male Exposure history: Not stated Non‐Covid group 1: Suspected group Source: Characteristics: Age: range 2 months to 64 years; no mean available Sex: 7/9 (78%) male Non‐Covid group 2: Negative group Source: Characteristics: Age: range 2 years to 94 years; no mean available Sex: 48/101 (48%) male
Index tests	Test name: [A] YHLO SARS‐COV‐2 IgM [B] YHLO SARS‐COV‐2 IgG Manufacturer: [A] [B] Shenzhen YHLO Biotech Co. Ltd. Antibody: [A] IgM, [B] IgG Antigen target: [A] [B] Nucleocapsid protein, spike‐protein Evaluation setting: Laboratory Test method: Chemiluminescence immunoassay (CLIA) Timing of samples: < 7 days after symptom onset: 12/68 (18%) 7‐14 days after symptom onset: 25/66 (37%) > 14 days after symptom onset: 31/68 (46%) Samples used: Serum Test operator: Unclear Definition of test positivity: Cut‐off value for positive was 10 arbitrary units/mL Blinding reported: Unclear Threshold predefined: Yes
Target condition and reference standard(s)	Reference standard: RT‐PCR detecting open reading frame lab (ORFlab) and nucleocapsid protein (N) genes Samples used: Not stated Timing of reference standard: Unclear Blinded to index test: Unclear Incorporated index test: No Definition of non‐COVID cases: As for cases; unclear if single or > 1 negative PCR result Samples used: Unclear Timing of reference standard: Unclear Blinded to index test: Unclear Incorporated index test: No; possibility that serology may have influenced final diagnosis of 9 suspect cases
Flow and timing	Time interval between index and reference tests: Unclear All patients received same reference standard: Yes Missing data: Nothing mentioned Uninterpretable results: Nothing mentioned Indeterminate results: Nothing mentioned Unit of analysis: Patients
Comparative
Notes	Funding: The author(s) received no financial support for the research, authorship, and/or publication of this article Publication status: Pre‐print (not peer reviewed) Source: medRxiv Author COI: The authors confirmed that there were 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?	Unclear
Was a case‐control design avoided?	Unclear
Did the study avoid inappropriate exclusions?	Unclear
Did the study avoid inappropriate inclusions?	Unclear
Could the selection of patients have introduced bias?		Unclear risk
Are there concerns that the included patients and setting do not match the review question?			Unclear
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?			Low concern
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
The reference standard does not incorporate the 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?	Unclear
Did all patients receive the same reference standard?	Yes
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