Chong 2021.

Study characteristics
Patient Sampling	Purpose: Diagnosis of current acute‐phase infection or current convalescent‐phase infection Design: Single‐group study to estimate sensitivity only [1] Confirmed COVID patients (63 samples from 18 patients) Recruitment: Not stated Prospective or retrospective: Retrospective Sample size: 63 (63) samples from 18 (18) patients Further detail: Patients diagnosed with COVID‐19 on the basis of a positive rt‐PCR and admitted to Kyushu University Hospital (Fukuoka, Japan) Exclusion criteria not stated
Patient characteristics and setting	Setting: Hospital inpatients Location: University Hospital, Fukuoka, Japan Country: Japan Dates: March and April 2020 Symptoms and severity: 5 asymptomatic 8 mild 3 severe 2 critical Demographics: Age: Mean 48.3 years (range 23‐69 years) Sex: 10 female, 8 male Exposure history: Not stated Non‐Covid group 1: NA Source: NA Characteristics: NA
Index tests	Test name: [A] 2019‐nCoV IgG/IgM Rapid Test Cassette Manufacturer: [A] Hangzhou Alltest Biotech Co. Ltd. Antibody: IgG and IgM Antigen target: Nucleocapsid protein Evaluation setting: POCT performed retrospectively in a laboratory Test method: Immunochromatographic assay Timing of samples: 1‐33 days post‐symptom onset or post‐positive PCR for asymptomatic cases: 1‐6 days: 8/63 samples 7‐13 days: 35/63 samples 14‐20 days: 11/63 samples 21‐33 days: 9/63 samples Samples used: Serum samples, remaining from other biochemical tests (retrospective analysis) Test operator: Not stated Definition of test positivity: The presence of anti‐SARS‐CoV‐2 IgM and/or IgG antibodies was separately indicated by a red line in the corresponding area of the device. Blinding reported: Not stated but only included COVID patients Threshold predefined: yes, visual‐based
Target condition and reference standard(s)	Reference standard: real‐time PCR assay performed by the Japanese Institute of Health according to the manual for the detection of pathogen 2019‐nCoV; threshold not stated Samples used: nasal and pharyngeal swab specimens Timing of reference standard: Not stated Blinded to index test: Yes, prior index test Incorporated index test: No Definition of non‐COVID cases: NA
Flow and timing	Time interval between index and reference tests: Not stated All patients received same reference standard: Yes Missing data: Not stated Uninterpretable results: Not stated Indeterminate results: Not stated Unit of analysis: Samples
Comparative
Notes	Funding: Not stated Publication status: Published paper Source: Influenza & Other Respiratory Viruses Author COI: "We have no financial conflicts of interest to declare."
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?	No
If a threshold was used, was it pre‐specified?	Yes
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?			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?	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