Whitman 2020b [A].

Study characteristics
Patient Sampling	Purpose: Diagnosis of acute‐phase infection Design: Two‐group study estimating sensitivity and specificity [1] SARS‐CoV‐2 RT‐PCR‐positive (n = 44) [2] pre‐pandemic asymptomatic adults (n = 30) [3] pre‐pandemic other infection controls with febrile and/or respiratory illness (n = 30) Recruitment: Not reported Prospective or retrospective: Not reported Sample size: 104 (44) Further detail: No further details
Patient characteristics and setting	Setting: Inpatient Location: Massachusetts General Hospital Country: USA Dates: Not stated Symptoms and severity: Not stated Demographics: Not stated Exposure history: Not stated Non‐Covid group 1: Pre‐pandemic, healthy Source: No further details Characteristics: Non‐Covid group 2: Pre‐pandemic, other infection controls Source: No further details Characteristics: No further details
Index tests	Test name: See below Manufacturer: [A] SD Biosensor ‐ Standard Q COVID‐19 IgM/IgG Duo (KT1032; lot P630C) [B] Biolidics ‐ 2019‐nCoV IgG/IgM antibody detection kit (CBB‐F015016‐V; V2020 0330) [C] Biomedomics ‐ COVID‐19 IgM and IgG Rapid Test (51‐002‐20; lot 20200, 22702, 20200, 32103) Antibody: IgG, IgM Antigen target: [A] N‐based [B] N‐ and S‐based [C] S‐based Evaluation setting: POC or laboratory Test method: LFA Timing of samples: Not stated Samples used: serum/plasma Test operator: Not stated Definition of test positivity: Not stated; assume as per manufacturer Blinding reported: Not reported Threshold predefined: Not stated; assume as per manufacturer
Target condition and reference standard(s)	Reference standard: RT‐PCR; threshold NR Samples used: Not stated Timing of reference standard: Not stated Blinded to index test: Yes; prior to index Incorporated index test: No Definition of non‐COVID cases: [2] + [3] Samples used: Not stated Timing of reference standard: [2] + [3] pre‐pandemic Blinded to index test: yes 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: None reported Uninterpretable results: None reported Indeterminate results: None reported Unit of analysis: Patients
Comparative
Notes	Funding: Not reported; presume as per main study reported in Whitman 2020 (A) Publication status: pre‐print Source: medRxiv Author COI: Not reported; presume as per main study reported in Whitman 2020 (A)
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?	No
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?	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?	Yes
Were results presented per patient?	Yes
Could the patient flow have introduced bias?		High risk