Theel 2020 [A].

Study characteristics
Patient Sampling	Purpose: To evaluate four high throughput serologic tests for detection of anti‐SARS‐CoV‐2 IgG antibodies Multi‐group study to estimate sensitivity and specificity for diagnosis of active disease/identification of previous disease Design: [1] serum samples from patients with confirmed COVID‐19 (n = 56, 224 samples) [2] healthy donor sera from 2018 (n = 149 samples) [3] cross‐reactivity serum panel collected in early 2020 (n = 105 samples, see comments) In group [1], 11 samples from outpatients would be excluded from our review as taken 0‐7 days post‐positive PCR. Recruitment: [1] Serum samples were collected as available throughout the hospital stay for the inpatient group until discharge, whereas prospective collection of acute and convalescent sera was completed for outpatients. [2] Samples collected in 2018, prior to the SARS‐CoV‐2 outbreak [3] Samples submitted for testing as part of routine clinical care in January and early February 2020 Prospective or retrospective: Mixed (as above) Sample size: 478 (224 samples from 56 patients) of which 476 (213 samples from 56 patients were eligible for our review). Further detail: Not stated
Patient characteristics and setting	Setting: Inpatients and outpatients Location: Division of Clinical Microbiology, Department of Laboratory Medicine, Mayo Clinic, Rochester, MN Country: USA Dates: [1] COVID cases March and April 2020 Symptoms and severity: 33 were hospitalised (inpatient group) and 23 were treated as outpatients (outpatient group) Demographics: Median age of the 33 inpatients was 61 years (range: 24 to 90 years) and 61% (20/33) were male. Among the 23 outpatients, the median age was 37 years (range: 21 to 64 years) and 43% (10/23) were male. Exposure history: Not stated Non‐Covid group 1: Healthy donors Source: Pre‐pandemic, 2018 Characteristics: Not stated Non‐Covid group 2: Cross‐reactivity Source: January and early February 2020 Characteristics: Not stated
Index tests	Test name: [A] Euroimmun Anti‐SARS‐CoV‐2 IgG ELISA [B] Epitope Novel Coronavirus COVID‐19 IgG ELISA [C] Abbott Laboratories SARS‐CoV‐2 IgG Chemiluminescent Microparticle Immunoassay [D] VITROS Anti‐SARS‐CoV‐2 IgG Chemiluminescent Immunoassay Manufacturer: [A] Euroimmun, Lübeck, Germany [B] Epitope Diagnostics Inc., San Diego, CA [C] Abbott Laboratories, Abbott Park, IL [D] Ortho‐Clinical Diagnostics, Rochester, NY Antibody: [A] IgG [B] IgG [C] IgG [D] IgG Antigen target: [A] S1‐protein from the SARS‐CoV‐2 spike‐protein [B] nucleocapsid protein from SARS‐CoV‐2 [C] SARS‐CoV‐2 nucleocapsid antigen [D] SARS‐CoV‐2 spike antigen Evaluation setting: [A] Laboratory, used in laboratory [B] Laboratory, used in laboratory [C] Laboratory, used in laboratory [D] Laboratory, used in laboratory Test method: [A] ELISA [B] ELISA [C] Chemiluminescent Microparticle Immunoassay (CMIA) [D] Chemiluminescent Immunoassay (CLIA) Timing of samples: Inpatients: 0 to 26 days post‐symptom onset Outpatients: 11 patients had both baseline and convalescent serum samples collected at 3 to 7 days and 20 to 31 days post‐initial positive SARS‐CoV‐2 RT‐PCR result, respectively, and the remaining 12 outpatients only had a convalescent sample collected. 33 inpatients (190 samples) 0‐7 days pso: 38 8‐14 days pso: 91 15‐26 days pso: 61 23 outpatients (34 samples): 0‐7 days post‐PCR+: 11 (excluded from review) 20‐31 days post‐PCR+: 23 Samples used: [1] Serum [2] Serum [3] Serum [4] Serum Test operator: Laboratory personnel Definition of test positivity: [A] Index values (signal to cut‐off [S/Co] ratios) of < 0.8, ≥ 0.8 to < 1.1, and ≥ 1.1 were interpreted as negative, indeterminate, and positive, respectively, per the instructions for use. [B] The qualitative index value (S/Co) cut‐off thresholds used for negative, indeterminate and positive results were < 1.01, ≥ 1.01 to < 1.21, and ≥ 1.21, respectively. [C] The patient sample signal was divided by the calibrator signal, with calculated signal to cut‐off (S/Co) values of < 1.4 and ≥ 1.4 reported as negative and positive, respectively. [D] The patient sample signal was divided by the calibrator signal, with calculated signal to cut‐off (S/Co) values of < 1.00 and ≥ 1.00 reported as negative and positive, respectively. Blinding reported: Not stated Threshold predefined: [A] Yes, per the instructions for use [B] No, laboratory‐determined cut‐off threshold. Modified to optimise assay specificity [C] Yes, per the instructions for use [D] Yes, per the instructions for use
Target condition and reference standard(s)	Reference standard: SARS‐CoV‐2 RT‐PCR assay (laboratory‐developed or commercially available FDA EUA) Samples used: nasopharyngeal swab Timing of reference standard: Not stated Blinded to index test: Yes, prior Incorporated index test: No Definition of non‐COVID cases: [2] Pre‐pandemic [3] Not stated Samples used: [2] Pre‐pandemic [3] Not stated Timing of reference standard: [2] Pre‐pandemic [3] Not stated Blinded to index test: Yes, prior Incorporated index test: No
Flow and timing	Time interval between index and reference tests: Inpatients: Not stated Outpatients: 11 patients had both baseline and convalescent serum samples collected at 3 to 7 days and 20 to 31 days post‐initial positive SARS‐CoV‐2 RT‐PCR result, respectively, and the remaining 12 outpatients only had a convalescent sample collected. All patients received same reference standard: No Missing data: Not stated Uninterpretable results: None reported Indeterminate results: For statistical analysis, indeterminate results by the Euroimmun and Epitope anti‐SARS‐CoV‐2 IgG ELISAs were considered ‘negative’. Unit of analysis: Samples
Comparative
Notes	Funding: Not stated Publication status: Accepted Manuscript Source: Journal of Clinical Microbiology, doi:10.1128/JCM.01243‐20 Author COI: Not stated
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?	No
Could the conduct or interpretation of the index test have introduced bias?		High 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?	Unclear
Did all participants receive a reference standard?	Unclear
Were results presented per patient?	No
Could the patient flow have introduced bias?		High risk