Kaneko 2021.

Study characteristics
Patient Sampling	Purpose: Diagnosis of current acute‐phase infection or current convalescent‐phase infection Design: Two‐group study to estimate sensitivity and specificity, [1] COVID‐19 patients (87 samples from 51 patients), [2] Pre‐pandemic controls (patients with other disease) (n = 100). Recruitment: Not stated Prospective or retrospective: [1] Prospective [2] Retrospective Sample size: 187 (87) samples Further detail: Inclusion ‐ [1] patients with acute COVID‐19 infection confirmed by RT‐PCR who were admitted to Musashino Red Cross Hospital and Tokyo Medical and Dental University Medical Hospital, between March and May 2020; [2] noninfected patients admitted to Musashino Red Cross Hospital and Tokyo Medical and Dental University Medical Hospital with other diseases in August and September 2019, before the spread of COVID‐19 infection. No exclusion criteria
Patient characteristics and setting	Setting: Hospital inpatient Location: Musashino Red Cross Hospital and Tokyo Medical and Dental University Medical Hospital Country: Japan Dates: March to May 2020 Symptoms and severity: All hospitalised All of the patients had clinical symptoms such as fever, cough, diarrhoea, malaise, and/or tachypnoea, no asymptomatic patients with COVID‐19. Demographics: median age 63 (25‐95) years, 37 (72.5%) male Exposure history: Not stated Non‐Covid group 1: Pre‐pandemic controls Source: Musashino Red Cross Hospital and Tokyo Medical and Dental University Medical Hospital, August to September 2019 Characteristics: Admitted for other disease, such as hepatitis C virus infection Non‐Covid group 2: NA Source: NA Characteristics: NA
Index tests	Test name: SARS‐Cov‐2 IgM/IgG Ab assay; 2019‐nCoV Ab Test Cassette (Colloidal Gold) Manufacturer: Innovita, Beijing, China Antibody: IgM/IgG Antigen target: antigen used not described Evaluation setting: POC test, unclear how it was used Test method: Lateral flow immunoassay (colloidal gold) (CGIA) Timing of samples: different time points 0‐4 days pso: 2/87 4‐7 days pso: 6/87 8‐14 days pso: 38/87 15‐28 days pso: 23/87 > 28 days pso: 18/87 Samples used: [1] Serum samples [2] serum samples stored at −80℃ Test operator: not stated Definition of test positivity: visible line The presence of only the control (C) line indicated a negative result; the presence of both the control line (C) and the IgM or IgG antibody (T) line indicated a positive result for IgM or IgG Ab, respectively. Blinding reported: No Threshold predefined: yes
Target condition and reference standard(s)	Reference standard: RT‐PCR for SARS‐CoV‐2 in accordance with the nationally recommended method in Japan. Samples used: Pharyngeal and nasopharyngeal swabs Timing of reference standard: not stated Blinded to index test: yes, prior index test Incorporated index test: no Definition of non‐COVID cases: Pre‐pandemic, other disease Samples used: None (pre‐pandemic) Timing of reference standard: pre‐pandemic Blinded to index test: yes (presumed based on timing) Incorporated index test: no
Flow and timing	Time interval between index and reference tests: Not stated All patients received same reference standard: No Missing data: Not stated Uninterpretable results: Not stated Indeterminate results: Not stated Unit of analysis: [1] Samples (87 samples from 51 patients) [2] Not stated (100 samples)
Comparative
Notes	Funding: Not stated Publication status: Published paper Source: Journal of Medical Virology 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?	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?	No
Were all patients included in the analysis?	Yes
Did all participants receive a reference standard?	Unclear
Were results presented per patient?	No
Could the patient flow have introduced bias?		High risk