Flower 2020 [C].

Study characteristics
Patient Sampling	See main entry for this study for characteristics and QUADAS‐2 assessment
Patient characteristics and setting	See main entry for this study for characteristics and QUADAS‐2 assessment
Index tests	Test name: Phase I: (A) Wondfo SARS‐CoV‐2 Antibody test (lateral flow method); (B) Menarini Zheijang Orient Gene (lateral flow); (C) Fortress Diagnostics COVID‐19 TOTAL Ab Device; (D) Biopanda COVID‐19 Rapid Antibody test; (E) Biosure COVID‐1 Antibody Self‐Test. Manufacturer: (A) Guangzhou Wondfo Biotech (Guangzhou, China); (B) Menarini Zhejiang Orient Gene Biotech Co Ltd; (C) Fortress Diagnostics; (D) Biopanda; (E) Biosure (Mologic). Antibody: (A) IgG/M combined; (B) IgG & M; (C) IgG & M; (D) IgG & M; (E) IgG only. Antigen target: (A) S; (B) S1, S2 and N; (C) S; D) S and N; (E) N. Evaluation setting: POCT performed as POCT and in lab for comparison Test method: Lateral flow immunoassay Timing of samples: After 21 days of symptom onset; median (q1, q3) duration = 44 (35‐53) days; range 21–100 days Samples used: LFIA self‐tests with finger‐prick capillary blood; provided on the same day venous whole blood and serum samples for laboratory analysis Test operator: Self‐test (participant interpretation) and observed by a member of the team (trained interpreter observation), finger prick participant self‐read and finger prick trained observer‐read Lab test on serum and whole blood samples: Initially, scoring was performed independently by two technicians, but this practice ceased after inter‐rater scoring was found to be almost perfect by 7‐point categorical score (Kappa = 0.81). Definition of test positivity: By the presence of IgG band (if two separate lines are there for IgG and IgM separately, n=3 kits OR if only one line to detect IgG only, n=1 kit) or presence of combined IgG + IgM band (n=1 kit). Manufacturer instructions were followed. Intensity of the result band(s) from 0 (negative) to 6 according to a standardised scoring system on a visual guide. Invalid tests were repeated. A photograph of the completed test was emailed to the study team. For consistency, in the three kits which had separate IgM and IgG bands ([B], [C], [D]), only IgG was counted as a positive result (i.e. ‘MG’ or ‘G’ but not ‘M’, distinct from manufacturer guidance). [E] Commercial Biosure kit comes in box with device holder and reading card. Clinic self‐tests in this study were performed with the device alone. Blinding reported: Yes for lab analyses, no for self‐test Threshold predefined: Yes
Target condition and reference standard(s)	See main entry for this study for characteristics and QUADAS‐2 assessment
Flow and timing	See main entry for this study for characteristics and QUADAS‐2 assessment
Comparative
Notes	See main entry for this study for characteristics and QUADAS‐2 assessment
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)
Were the index test results interpreted without knowledge of the results of the reference standard?
If a threshold was used, was it pre‐specified?
Could the conduct or interpretation of the index test have introduced bias?
Are there concerns that the index test, its conduct, or interpretation differ from the review question?
DOMAIN 2: Index Test (Antibody tests)
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?	No
Were results presented per patient?	Unclear
Could the patient flow have introduced bias?		High risk