Merrill 2020 [A].

Study characteristics
Patient Sampling	Purpose: Diagnosis of current acute‐phase infection or current convalescent‐phase infection Design: Multi‐group study to estimate sensitivity and specificity [1] Confirmed COVID‐patients (54 specimens from 32 unique patients) [2] Suspected COVID cases and/or potential cross‐reactive with negative PCR (n = 35) [3] Pre‐pandemic samples (n = 139) Recruitment: Not stated Prospective or retrospective: [1]‐[3] Retrospective Sample size: 228 (54) of which 204‐210 (30‐36) were included in our review Further detail: Inclusion: [1] and [2] Remnant clinical specimens from individuals with SARS‐CoV‐2 PCR performed at our institution [3] Specimens collected prior to December 2019 for research and/or clinical assay validation studies Exclusions not stated
Patient characteristics and setting	Setting: Unclear (inpatients and outpatients?) Location: University of Iowa Hospitals and Clinics (UIHC), Iowa City, Iowa, USA Country: Iowa, USA Dates: Not stated Symptoms and severity: 13 asymptomatic; 41 symptomatic Demographics: Not stated Exposure history: Not stated Non‐Covid group 1: [2] Current, PCR‐negative (COVID suspects or cross‐reactive) Source: University of Iowa Hospitals and Clinics (UIHC), Iowa City, Iowa, USA. Time not stated Characteristics: Asymptomatic n = 4; symptomatic n = 10 Other coronaviruses (229E, HKU1, NL63, OC43), n = 8 Respiratory pathogens: adenovirus n = 2, metapneumovirus n = 1, pneumocystis n = 1, rhinovirus/enterovirus n = 1, Or antibodies to other viruses: HAV n = 1, HBV/HCV n = 4, EBV/CMV n = 2, RF n = 1 Non‐Covid group 2: [3] Pre‐pandemic, healthy or other diseases Source: University of Iowa Hospitals and Clinics (UIHC), Iowa City, Iowa, USA. Before December 2019 Characteristics: HIV n = 12 No other diseases: n = 127
Index tests	Test name: [A] DiaSorin Liaison SARS‐CoV‐2 S1/S2 IgG [B] Roche Diagnostics Elecsys Anti‐SARS‐COV‐2 assay Manufacturer: [A] DiaSorin [B] Roche Antibody: [A] IgG [B] total antibodies (IgG, IgM, IgA) Antigen target: [A] S1 and S2 domains of the spike (S)‐protein [B] Nucleocapsid (N)‐protein Evaluation setting: [A] and [B] Laboratory Test method: [A] chemiluminescent immunoassay [B] electrochemiluminescence immunoassay Timing of samples: < 7 days pso: 5/54 7‐13 days pso: 12/54 > 13 days pso: 12/54 Unknown: 12/54 Asymptomatic: 13/54 < 7 days post‐PCR+: 35/54 7‐13 days post‐PCR+: 13/54 > 13 days post‐PCR+: 6/54 Samples used: Plasma samples (lithium heparin and EDTA) Test operator: Not stated (possibly lab personnel at the Department of Pathology) Definition of test positivity: [A] signal of 15 AU/mL or higher indicating a positive result [B] cut‐off index (COI) of 1.0 or higher indicating a positive result Blinding reported: Not stated Threshold predefined: yes
Target condition and reference standard(s)	Reference standard: rt‐PCR, threshold not stated Samples used: Not stated Timing of reference standard: Not stated Blinded to index test: yes, prior to index test Incorporated index test: no Definition of non‐COVID cases: [2] rt‐PCR, threshold not stated [3] Pre‐pandemic Samples used: [2] Not stated [3] Pre‐pandemic Timing of reference standard: [2] Not stated [3] Pre‐pandemic Blinded to index test: yes, prior to index test Incorporated index test: no
Flow and timing	Time interval between index and reference tests: [1] < 7 days post‐PCR+: 35/54 7‐13 days post‐PCR+: 13/54 > 13 days post‐PCR+: 6/54 [2] and [3] Not stated All patients received same reference standard: No Missing data: yes (our review excluded 12 samples that were > 13 days pso and 12 samples but included the group > 13 days post‐positive PCR. Unclear how the 6 samples > 13 days post‐positive PCR overlap with the other groups) Uninterpretable results: Not stated Indeterminate results: Possibly none as no borderline range Unit of analysis: Samples
Comparative
Notes	Funding: No sponsor was declared Publication status: Published paper Source: Journal of Applied Laboratory Medicine Author COI: No authors declared any 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?	No
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?		High 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?	No
Did all participants receive a reference standard?	Yes
Were results presented per patient?	No
Could the patient flow have introduced bias?		High risk