Patel 2021 [A].

Study characteristics
Patient Sampling	Purpose: Diagnosis of convalescent‐phase infection Design: Two‐group study to assess sensitivity and specificity for 5 commercially available serology assays [1] Covid‐19 convalescent plasma donors (n = 214 potential) [2] Pre‐pandemic samples from emergency department patients (n = 1099) Recruitment: Not stated Prospective or retrospective: Retrospective Sample size: 1313 (214) Further detail: Inclusion: [1] Stored plasma specimens from a "convenience sample" of potential CCP donors that were recruited in the Baltimore, MD and Washington, DC areas from April 2020 to July 2020. Individuals were eligible for enrolment if they had a documented history of a positive molecular assay test result for SARS‐CoV‐2 infection and met standard self‐reported eligibility criteria for blood donation. [2] Stored serum specimens from an identity‐unlinked HIV serosurvey conducted in 2016 among adult patients attending the Johns Hopkins Hospital Emergency Department Exclusion: Not stated
Patient characteristics and setting	Setting: Community Location: Baltimore MD and Washington DC area Country: USA Dates: April 2020‐July 2020 Symptoms and severity: 16/214 required hospitalisation Demographics: Different samples used for different assays: [A]‐ n = 146, median age (IQR) = 41 (29‐53), male n (%) = 78 (53.4), white race n (%) = 112 (76.7), hospitalised n (%) = 12 (8.2), median days since PCR‐positive test (IQR) = 44 (39‐51) [B]‐ n = 146, median age (IQR) = 41 (29‐53), male n (%) = 78 (53.4), white race n (%) = 112 (76.7), hospitalised n (%) = 12 (8.2), median days since PCR‐positive test (IQR) = 44 (39‐51) [C]‐ n = 140, median age (IQR) = 40 (29‐53), male n (%) = 76 (54.3), white race n (%) = 108 (77.1), hospitalised n (%) = 12 (8.6), median days since PCR‐positive test (IQR) = 44 (38‐50) [D]‐ n = 146, median age (IQR) = 41 (29‐53), male n (%) = 78 (53.4), white race n (%) = 112 (76.7), hospitalised n (%) = 12 (8.2), median days since PCR‐positive test (IQR) = 44 (39‐51) [E]‐ n = 214, median age (IQR) = 44 (33‐56), male n (%) = 110 (51.4), white race n (%) = 165 (77.1), hospitalised n (%) = 16 (7.5), median days since PCR‐positive test (IQR) = 46 (39‐57) Exposure history: Not stated Non‐Covid group 1: Pre‐pandemic controls Source: Stored serum specimens from an identity‐unlinked HIV serosurvey conducted in 2016 among adult patients attending the Johns Hopkins Hospital Emergency Department Characteristics: Different samples used for different assays: [A]‐ n = 561; median age (IQR) = 49 (32‐60); male n (%) = 247 (44.0); race/ethnicity: Non‐Hispanic white n (%) = 161 (28.7), Non‐Hispanic black n (%) = 345 (61.5), Hispanic n (%) = 19 (3.4), non‐Hispanic Asian n (%) = 10 (1.8), other n (%) = 26 (4.6); HIV Ab‐positive n (%) = 22 (3.9) [B]‐ n = 577; median age (IQR) = 48 (32‐60); male n (%) = 251 (43.5); race/ethnicity: Non‐Hispanic white n (%) = 166 (28.8), Non‐Hispanic black n (%) = 353 (61.2), Hispanic n (%) = 21 (3.6), non‐Hispanic Asian n (%) = 10 (1.7), other n (%) = 27 (4.7); HIV Ab‐positive n (%) = 26 (4.5) [C]‐ n = 306; median age (IQR) = 47 (31‐59); male n (%) = 135 (44.1); race/ethnicity: Non‐Hispanic white n (%) = 80 (26.1), Non‐Hispanic black n (%) = 191 (62.4), Hispanic n (%) = 12 (3.9), non‐Hispanic Asian n (%) = 7 (2.3), other n (%) = 16 (5.2); HIV Ab‐positive n (%) = 19 (6.1) [D]‐ n = 498; median age (IQR) = 45 (30‐59); male n (%) = 209 (42.0); race/ethnicity: Non‐Hispanic white n (%) = 130 (26.1), Non‐Hispanic black n (%) = 313 (62.9), Hispanic n (%) = 29 (5.8), non‐Hispanic Asian n (%) = 6 (1.2), other n (%) = 20 (4.0); HIV Ab‐positive n (%) = 19 (3.8) [E]‐ n = 498; median age (IQR) = 45 (30‐59); male n (%) = 209 (42.0); race/ethnicity: Non‐Hispanic white n (%) = 130 (26.1), Non‐Hispanic black n (%) = 313 (62.9), Hispanic n (%) = 29 (5.8), non‐Hispanic Asian n (%) = 6 (1.2), other n (%) = 20 (4.0); HIV Ab‐positive n (%) = 19 (3.8)
Index tests	Test name: [A]‐ Anti‐SARS‐CoV‐2 ELISA (IgG) [B]‐ EDI novel coronavirus COVID‐19 IgG ELISA kit [C]‐ SARS‐CoV‐2 NP IgG ELISA kit [D]‐ Abbott‐Architect SARS‐CoV‐2 IgG assay [E]‐ Elecsys anti‐SARS‐CoV‐2 Manufacturer: [A]‐ Euroimmun, Lubeck, Germany [B]‐ Epitope Diagnostics, Inc. (EDI), San Diego, CA, USA [C]‐ ImmunoDiagnostics Limited, Sha Tin, Hong Kong [D]‐ Abbott Laboratories Inc., Abbott Park, IL, USA [E]‐ Roche Diagnostics, Indianapolis, IN, USA Antibody: [A] to [D] ‐ IgG; [E]‐ Total Antibodies Antigen target: [A]‐ Spike 1‐Protein; [B] to [E] ‐ Nucleocapsid Protein Evaluation setting: Laboratory tests in laboratory Test method: [A] to [C] ‐ Manual ELISA [D]‐ Chemiluminescent microparticle immunoassay (CMIA) [E]‐ Electrochemiluminescence assay (ECLIA) Timing of samples: 38‐57 days post‐PCR + Samples used: Plasma/serum Test operator: Not stated Definition of test positivity: [A]‐ Negative, S/C ratio < 0.8; borderline, S/C ratio => 0.8 & < 1.1; positive, S/C ratio => 1.1 [B]‐ Negative, OD‐n =< 0.18; borderline, OD‐n > 0.18 & < 0.22; positive, OD‐n => 0.22 [C]‐ Negative, OD‐n < 0.15; borderline, OD‐n => 0.25 & =< 0.50; positive, OD‐n > 0.50 [D]‐ Negative, index (S/C) < 1.40; positive, index (S/C) => 1.40 [E]‐ Nonreactive, index < 1.0; reactive => 1.0 Borderline results considered seronegative Threshold predefined: Yes, manufacturer's cut‐off values used
Target condition and reference standard(s)	Reference standard: Positive molecular assay test Samples used: Not stated. Timing of reference standard: Not stated. Blinded to index test: Yes, based on timing of test (prior molecular confirmation of SARS‐CoV2 infection was required to be recruited to COVID‐19 group). Incorporated index test: No Definition of non‐COVID cases: Pre‐pandemic samples Samples used: NA Timing of reference standard: Pre‐pandemic controls Blinded to index test: Yes, as based on pre‐pandemic controls Incorporated index test: No
Flow and timing	Time interval between index and reference tests: [A]‐ Median days since PCR+ test (IQR)‐ 44 (39‐51) [B]‐ Median days since PCR+ test (IQR)‐ 44 (39‐51) [C]‐ Median days since PCR+ test (IQR)‐ 44 (38‐50) [D]‐ Median days since PCR+ test (IQR)‐ 44 (39‐51) [E]‐ Median days since PCR+ test (IQR)‐ 46 (39‐57) All patients received same reference standard: No Missing data: All 214 Covid samples tested only on [E] Uninterpretable results: Not stated Indeterminate results: Borderline/indeterminate results treated as seronegative Unit of analysis: Patients. No individual contributed multiple specimens
Comparative
Notes	Funding: This work was supported in part by the Division of Intramural Research, National Institute of Allergy and Infectious Diseases (NIAID), as well as by extramural support from NIAID and NIH Center of Excellence in Influenza Research and Surveillance; National Heart Lung and Blood Institute; National Institute of Drug Abuse; Bloomberg Philanthropies; and the Department of Defense. Publication status: Published paper Source: Journal of Clinical Microbiology Author COI: Authors declared no potential conflicts of interest.
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?	Unclear
Did all participants receive a reference standard?	Yes
Were results presented per patient?	Yes
Could the patient flow have introduced bias?		High risk