Gao 2020b [A].

Study characteristics
Patient Sampling	Single‐group study recruiting patients estimating sensitivity [1] confirmed COVID‐19 cases Recruitment: consecutive (inferred). From all confirmed cases admitted to hospital Prospective or retrospective recruitment of cases: retrospective (appeared) Sample size (virus/COVID cases): 22 participants (corresponding to 37 samples) Inclusion and exclusion criteria: not clearly defined; described all participants having typical ground‐glass opacity of the lung on CT but not clear if this was part of eligibility
Patient characteristics and setting	Setting: hospital inpatient Location: Fifth Hospital of Shijiazhuang Country: China Dates: from 21 January‐24 February 2020 Symptoms and severity: typical ground‐glass opacity in lung was observed in CT scan results of all participants. At the time the paper was written all participants had recovered and been discharged from hospital. Sex: 14/22 male (64%) Age: 40 (4‐72) years Exposure history: 11 participants had recent history of travel to epidemic areas, and the remaining 10 had close contacts with their family members, who were confirmed to be infected by 2019‐nCoV.
Index tests	Gao 2020b [A] is test [A] from the following entry: Test name: [A] CLIA; [B] GICA; [C] ELISA Manufacturer: Beier Bioengineering Company (Beijing, China) Ab targets: IgG and IgM Antigens used: spike (S) and nucleocapsid (N) proteins of 2019‐nCoV Test method: [A] CLIA; [B] GICA; [C] ELISA Timing of samples: [1] early stage (1‐7 days pso) 10/37 samples (27%), [2] middle stage (8‐14 days pso) 13/37 samples (35%); [3] late stage (14‐24 days pso) 14/37 samples (38%) Samples used: serum Test operators: laboratory staff Definition of test positivity: [A] samples with an concentration ≥ 8 arbitrary unit (AU)/mL were considered positive. [B] Visible line [C] The absorbance at 450 nm (A450 nm) of each well was determined and the cut‐off value was 0.10 + A negative control. A value > cut‐off value was considered a positive result. Blinded to reference standard: NR Threshold predefined: [A] samples with an concentration ≥ 8 arbitrary unit (AU)/mL were considered positive. [B] Positive results showed the appearance of both control line and testing line. [C] The absorbance at 450 nm (A450 nm) of each well was determined and the cut‐off value was 0.10 + A negative control. A value > cut‐off value was considered a positive result.
Target condition and reference standard(s)	Reference standard for cases: RT‐PCR assay (2019‐nCoV RNA Test Kit, Daan Gene Company, China) Samples used: nasal and pharyngeal swab specimens Timing of reference standard: on admission (most likely) Blinded to index test: yes, index tests performed on already‐confirmed cases (inferred) Incorporated index test: no Reference standard for non‐cases: NA
Flow and timing	Time interval between index and reference tests: NR Results presented by time period: yes All participants received the same reference standard: yes Missing data: timing of reference standard test Uninterpretable results: Indeterminate results: Unit of analysis: samples
Comparative
Notes	Funding: NR Publication status: published letter Source: Chinese Medical Journal Study author COI: none
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Yes
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?			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?			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?	No
Could the patient flow have introduced bias?		High risk