Hamilton 2020.

Study characteristics
Patient Sampling	Purpose: Diagnosis of current acute and convalescent‐phase infection Design: A multi‐group study with three groups to estimate sensitivity and specificity: [1] patients with laboratory confirmed or clinically suspected COVID‐19 enrolled into DISCOVER study (n = 149): [1a] 114 PCR+ hospitalised COVID patients; [1b] 35 PCR‐, clinically diagnosed hospitalised COVID patients); [2] healthcare workers at North Bristol NHS Trust with laboratory confirmed COVID‐19 (n = 114); [3] pre‐pandemic respiratory infection controls (n = 20). Group [3] not eligible for our review as < 25 samples leaving a "Single‐group study to estimate sensitivity". Recruitment: [1] For the DISCOVER cohort, patients with confirmed (PCR+) and suspected (PCR‐) COVID‐19 were prospectively recruited and samples were taken on admission; [2] all healthcare worker who had received a positive PCR for SARS‐CoV‐2 at the PHE South West regional virology laboratory and went on to have antibody testing as part of as part of NHS England’s strategy for healthcare worker antibody testing; [3] pre‐pandemic plasma samples of patients with respiratory infection from an established tissue bank (pleural investigation database). Prospective or retrospective: Group [1] prospective; Group [2] unclear; Group [3] retrospective. Sample size: 283 (263) samples of which 263 (263) were eligible for our review Further detail: [1] Patients with COVID‐19 enrolled into the DISCOVER study (PCR+ or clinically diagnosed); [2] Healthcare worker at North Bristol NHS Trust with laboratory confirmed COVID‐19 (positive PCR for SARS‐CoV‐2) and antibody testing as part of as part of NHS England’s strategy for healthcare worker antibody testing; [3] Pre‐pandemic plasma samples of patients with respiratory infection from the Pleural Investigation Database. No further details on exclusions but [1] 18 excluded from DISCOVER cohort; [2] 52 healthcare workers excluded.
Patient characteristics and setting	Setting: [1] Hospitalised patients with COVID‐19 [2] Convalescent (majority had not been hospitalised) Location: [1] An NHS hospital in the UK (Southmead Hospital, Bristol) [2] North Bristol NHS Trust ‐ PCR performed in the PHE southwest regional virology lab Country: UK Dates: Not reported Symptoms and severity: [1] mixed severity (all hospitalised);13 patients (8%) intensive care; 15 patients (9%) died; [2] Predominantly mild COVID‐19 (aware of fewer than 5 hospitalised patients). Demographics: [1] Median age 58 years, sex not reported; [2] Age or sex not reported Exposure history: [1] Not reported [2] Healthcare workers Non‐Covid group 1: NA
Index tests	Test name: Abbott Architect SARS‐CoV‐2 IgG assay Manufacturer: Abbott Antibody: IgG Antigen target: Not reported Evaluation setting: Laboratory Test method: Not reported (Architect platform) Timing of samples: [1] Time was calculated from reported symptom onset date. Median time unclear. < 5 days pso: 18/149 5‐9 days pso: 57/149 10‐14 days pso: 28/149 15‐20 days pso: 14/149 > 20 days pso: 32/149 > 42 days pso: 30/149 [2] Timing was calculated from the time of the positive PCR test. Median time to test 45 days (range 32‐51 days) Samples used: EDTA plasma (either fresh or stored at −80 C) Test operator: Not reported Definition of test positivity: According to manufacturer protocol Blinding reported: Not reported Threshold predefined: Not reported
Target condition and reference standard(s)	Reference standard: [1a] and [2] RT‐PCR [1b] "Clinical diagnosis" Samples used: Not reported Timing of reference standard: Not reported Blinded to index test: Yes Incorporated index test: No Definition of non‐COVID cases: NA
Flow and timing	Time interval between index and reference tests: [1] Not reported [2] Median time 45 days (range 32‐51 days) post‐positive PCR: > 20 days: 114/114 > 42 days: 66/114 All patients received same reference standard: No Missing data: Not stated Uninterpretable results: Not reported Indeterminate results: Not reported Unit of analysis: Samples
Comparative
Notes	Funding: Not reported Publication status: Published letter Source: Journal of Infection Author COI: Not reported
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Yes
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?	Unclear
If a threshold was used, was it pre‐specified?	Unclear
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?	Unclear
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?		Unclear 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