Criscuolo 2020 [A].

Study characteristics
Patient Sampling	Purpose: Assessment of clinical performance of two antibody tests for SARS‐CoV‐2 infection Design: Two‐group study estimating both sensitivity and specificity Group [1]: Lab‐confirmed cases of SARS‐CoV‐2 infection (n = 46). Group [2]: Pre‐pandemic controls (n = 85) For Group [1], lab confirmation likely referred to PCR test, but this was not explicitly stated. Recruitment: Random (approach not explained) Prospective or retrospective: Retrospective Sample size: 131 (46) Further detail: No more details available
Patient characteristics and setting	Setting: Inpatient service (all patients were hospitalised) Location: IRCCS San Raffaele Hospital, Milan Country: Italy Dates: Not stated Symptoms and severity: Not stated, all admitted Demographics: Not stated Exposure history: Not stated Non‐Covid group 1: Group [2]: Pre‐pandemic controls Source: Lab stocked samples collected between 2012 and 2018 Characteristics: Not stated
Index tests	Test name: [A] Elecsys Anti‐SARS‐CoV‐2 [B] LIAISON® SARS‐CoV‐2 69 S1/S2 IgG assay Manufacturer: [A] Roche Diagnostics [B] DiaSorin, Italy Antibody: [A] Total antibodies [B] IgG Antigen target: [A] N‐protein [B] S1 and S2 domains of the spike‐protein Evaluation setting: [A], [B]: Lab tests, done in lab Test method: [A] Electrochemiluminescence immunoassay (ECLIA) [B] Chemiluminescence immunoassay (CLIA) Timing of samples: For each patient: one serum sample collected at hospital admission and another one 15 days later. Time since symptom onset not reported. Samples used: Serum Test operator: Not stated Definition of test positivity: [A] Positive if COI >= 1 [B] Positive if > 15 AU/mL; undetermined if 12‐15 AU/mL; negative if < 12 AU/mL Blinding reported: Not stated Threshold predefined: Yes, as per manufacturer
Target condition and reference standard(s)	Reference standard: Apparently RT‐PCR (the authors only reported "lab‐confirmation"). No more details available Samples used: Not stated Timing of reference standard: Not stated Blinded to index test: Yes (done earlier) Incorporated index test: No Definition of non‐COVID cases: Pre‐pandemic samples ‐ no testing Samples used: NA Timing of reference standard: NA 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: Unclear: all cases (Group [1]) were lab‐confirmed but various assays were likely used. Missing data: None Uninterpretable results: None Indeterminate results: Yes, 1 for test [B] on pre‐pandemic samples (Group [2]); none reported for cases. Unit of analysis: Patients
Comparative
Notes	Funding: None reported Publication status: Pre‐print article Source: Pre‐print server (medRxiv) Author COI: None 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?	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?			Unclear
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