Boukli 2020 [A].

Study characteristics
Patient Sampling	Purpose: Diagnosis of current acute‐phase infection, and current convalescent‐phase infection Design: Multi‐group study to estimate sensitivity and specificity, including: [1] PCR‐positive Covid‐19 patients in intensive care unit (76 samples from 49 patients) [2] PCR‐positive Covid‐19 patients, described as 'unselected' (68 samples from 68 patients) [3] 'unselected' pre‐pandemic samples (n = 40) [4] pre‐pandemic samples from cases with other infection (n = 60) Results are presented for group [1] and [2] combined, and separately for group [3] and [4]. Reported results suggest that not all samples were tested with both assays. Recruitment: Unclear Prospective or retrospective: Retrospective Sample size: 217 (117) Further detail: Not further described
Patient characteristics and setting	Setting: Mixed; included hospital inpatient (Intensive care unit) and an unspecified setting Location: Saint‐Antoine Hospital, Paris Country: France Dates: Not stated Symptoms and severity: Not stated; 68/144 COVID‐19 samples from individuals in ICU Demographics: Not stated Exposure history: Not stated Non‐Covid group 1: Pre‐pandemic other infection Source: Pre‐pandemic Characteristics: Coronavirus 229E, NL63, OC43 (n = 10); primary CMV (n = 5); primary EBV (n = 10); acute HAV (n = 5); acute HBV (n = 4); acute HCV (n = 3); acute HEV (n = 5); acute HIV (n = 5); influenza A/B (n = 10); acute malaria (n = 3) Non‐Covid group 2: Pre‐pandemic 'unselected' samples Source: Pre‐pandemic Characteristics: No further details
Index tests	Test name: [A] Liaison SARS‐CoV‐2 S1/S2 IgG assay; [B] Alinity I SARS‐CoV‐2 IgG assay Manufacturer: [A] DiaSorin, Antony, France [B] Abbott Diagnostics, Rungis, France Antibody: [A] and [B] IgG Antigen target: [A] Recombinant S1 and S2 proteins; [B] capsid antigen Evaluation setting: Laboratory based Test method: CLIA Timing of samples: Not stated Day 1 to day 30 pso Samples used: Group [2], [3], [4] serum, Group [1] plasma; samples stored at ‐20 or ‐80°C Test operator: Not stated Definition of test positivity: [A] Negative was defined as < 12 absorbance units (AU)/mL, positive as > 15 AU/mL, and equivocal as 12 to 15 AU/mL; [B] positive was defined as > 1.4 index, negative was defined as < 1.4 index Equivocal results were re‐tested Blinding reported: Not stated Threshold predefined: Yes, as per manufacturer
Target condition and reference standard(s)	Reference standard: RT‐PCR; no further details Samples used: Not stated Timing of reference standard: During hospital stay in 49 cases. The rest unclear Blinded to index test: Not stated Incorporated index test: No Definition of non‐COVID cases: RT‐PCR‐negative Pre‐pandemic samples used Samples used: Not stated Timing of reference standard: Not stated Blinded to index test: Not stated Incorporated index test: No
Flow and timing	Time interval between index and reference tests: Not stated All patients received same reference standard: No (pre‐pandemic did not have SARS‐CoV‐2 PCR) Missing data: None reported Uninterpretable results: None reported Indeterminate results: None reported Unit of analysis: Samples
Comparative
Notes	Funding: No funding statement reported Publication status: Published letter Source: Journal of Clinical Microbiology Author COI: No COI statement reported
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?	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?	Unclear
Did all participants receive a reference standard?	Yes
Were results presented per patient?	No
Could the patient flow have introduced bias?		High risk