Xiang 2020a.

Study characteristics
Patient Sampling	Purpose: Two‐group study recruiting patients estimating sensitivity and specificity Design: PCR conducted for patients presenting with a history of travel to or residence in Wuhan or local endemic areas; [1] 85 RT‐PCR‐confirmed cases [2] 24 suspected cases with ≥ 2 negative RT‐PCR and none positive (and protocol is to retest RT‐PCR‐negatives every 1‐2 days) [3] 60 healthy blood donors (control group) (hospital staff) or from patients with other lung diseases in the same hospital (all PCR‐negative) Recruitment: NR Prospective or retrospective recruitment of cases: unclear Sample size (virus/COVID cases): 169 (109; data for 66 lab‐confirmed and 24 suspected cases extracted as D+ group) Inclusion and exclusion criteria: unclear
Patient characteristics and setting	Setting: hospital inpatients Location: Wuhan Country: China Dates: 19 January‐2 March 2020 Symptoms and severity: [1] severe 18/85 (21%) [2] 2/24 (8%) severe Sex: [1] female 54/85 (64%) [2] female 12/24 (50%) [3] 35/60 (58%) female Age: [1] median 51 (IQR 32‐65) [2] median 44 (IQR 36‐61) [3] median 34 (IQR 29‐51) Exposure history: NR
Index tests	Test name: Zhuhai Livzon SARS‐CoV‐2 ELISA Manufacturer: ELISA kits, Livzon Inc, Zhuhai, P.R.China, lot number of IgM: 20200308, IgG: 20200308 Ab targets: IgG IgM Antigens used: N‐protein Test method: ELISA Timing of samples: NR Samples used: serum Test operators: NR Definition of test positivity: unclear ‐ "The optical density of each well was determined by a microplate reader set to 450 nm within 30 min. The ratio of optical density to the cut‐off value (optical density of the blank well + 0.1) was reported as the Ab concentration. For detection of IgG, the dilution factor was changed (1:20) and the cut off value was modified (optical density of the blank well + 0.13)." Blinded to reference standard: no Threshold predefined: unclear
Target condition and reference standard(s)	Reference standard for cases: [1] RT‐PCR [2] Symptoms and PCR‐negative (no guideline cited but criteria clearly elaborated) Samples used: NP and/or OP swabs Timing of reference standard: NR Blinded to index test: yes Incorporated index test: no Reference standard for non‐cases: (no exposure or symptoms) and RT‐PCR‐negative
Flow and timing	Time interval between index and reference tests: NR Results presented by time period: no All participants received the same reference standard: Missing data: data per sample were provided for the 85 confirmed cases, however per participant data were available only for 66/85 confirmed cases plus 24/24 suspected cases (total number of cases reported = 90) Uninterpretable results: NR Indeterminate results: NR Unit of analysis: reported both samples and participants
Comparative
Notes	Funding: this work is funded by National Natural Science Foundation of China (No. 81973990, 91643101), and Science Foundation of Huazhong University of Science and Technology (No. 2020kfyXGYJ100). Publication status: published in journal Source: Infectious Disease Society of America Study author COI: declared that they have none
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	No
Was a case‐control design avoided?	No
Did the study avoid inappropriate exclusions?	Unclear
Did the study avoid inappropriate inclusions?	Yes
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?	No
If a threshold was used, was it pre‐specified?	Unclear
Could the conduct or interpretation of the index test have introduced bias?		High 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?	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?			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?	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