Paiva 2021 [A].

Study characteristics
Patient Sampling	Purpose: Multi‐group study to estimate sensitivity and specificity for diagnosis of active disease Design: [1] RT‐PCR‐positive COVID‐19 cases (n = 71, 113 samples) [2] Healthy individuals (n = 126) [3] Samples positive for other viruses and pathogens (to test cross‐reaction of the assays) (n = 119) [4] serum or plasma samples collected before the pandemic started in the United States (n = 942) Recruitment: [1] Remnant/discarded serum or plasma samples were collected from the Clinical Immunology Lab at a major academic pathology department [2] Recruitment unclear ‐ random at pre‐employment screening (table 3) [3] Unclear ‐ probably also from the same laboratory as the COVID‐19 samples [4] Pre‐pandemic: 500 samples originally for reference range determination of a troponin assay, 371 prenatal samples for reference range determination of quadruple tests, 50 pre‐pandemic samples from transfusion service and 21 pre‐pandemic plasma segments from the Rhode Island Blood Center. Prospective or retrospective: Retrospective Sample size: 1300 (113) (samples) Further detail: Not stated
Patient characteristics and setting	Setting: Hospital inpatients Location: Lifespan Health System (including Rhode Island Hospital and The Miriam Hospital, Providence, Rhode Island) Country: USA Dates: After 12 March 2020 Symptoms and severity: Highest level of treatment: Room air 26%; nasal cannula 45%; intubation 27%; extracorporeal membrane oxygenation 1% Demographics: 41% female; mean age 59.5 ± 1.9 White or Caucasian: 38/71 (53%) Hispanic or Latino: 22/71 (31%) African‐American: 10 (14%) Asian: 1/71 (1%) Exposure history: Not stated Non‐Covid group 1: [2] Current healthy controls Source: Pre‐employment screening before 12 March 2020 (early March 2020) Characteristics: Not stated Non‐Covid group 2: [3] Current, other viruses and pathogens [4] Pre‐pandemic healthy controls Source: [3] Collected from later March to early April 2020 [4] Collected before the pandemic started in the United States (before January 2020): Collected originally for: troponin study, prenatal plasma for quadruple test, transfusion service, Rhode Island Blood Center Characteristics: [3] The set included samples from patients testing positive for upper respiratory viruses and samples known to contain antibodies such as rheumatoid factor (RF), anti‐double stranded NA (ds‐DNA), antinuclear antibody (ANA), and paraprotein IgM and IgG Seasonal coronaviruses (n = 21): Other upper respiratory tract viruses (n = 27; influenza, metapneumovirus, rhinovirus/enterovirus, respiratory syncytial viruses and adenovirus) Samples with positive IgG or IgM against varicella zoster virus, rubella, Epstein‐Barr virus, cytomegalovirus (CMV) and hepatitis viruses (n = 71) [4] Not stated
Index tests	Test name: [A] SARS‐CoV‐2 Total Antibody Test [B] STANDARD Q COVID‐ 19 IgM/IgG Duo Test [C] SARS‐CoV‐2 IgG test Manufacturer: [A] Wondfo, Guangzhou, China [B] SD Biosensor, Gyeonggi‐do, Korea [C] Abbott Diagnostics, Lake Forest, IL Antibody: [A] Total antibody (IgM and IgG) [B] IgM/IgG [C] IgG Antigen target: [A] Spike‐protein [B] Not stated [C] Nucleocapsid protein Evaluation setting: [A] POC, used in laboratory [B] POC, used in laboratory [C] Laboratory test, used in laboratory Test method: [A] Lateral flow assay (no further detail) [B] Lateral flow assay (no further detail) [C] Chemiluminescent assay Timing of samples: [1] 1‐35 (38) days post‐symptom onset (mean 11.2) [2] NA [3] Unclear [4] NA Samples used: [A, B, C] serum (n = 16) or plasma (n = 97) for [1], serum for [2] and [3], plasma for [4] Test operator: [A] and [B] The reading was performed by three investigators (KJP, EWT, and SL) affiliated to the Department of Pathology and Laboratory Medicine, Warren Alpert Medical School of Brown University. Definition of test positivity: [A] and [B] positive result was indicated by a visible band in the designated area accompanied with an appropriate control band. The reading was performed by three investigators; consensus for any ambiguous results was obtained by at least two investigators. [3] Samples with signal‐to‐cut‐off (S/CO) ratio greater than or equal to 1.4 were considered positive. Blinding reported: Unclear Threshold predefined: Yes, by manufacturers
Target condition and reference standard(s)	Reference standard: RT‐PCR [ePlex® SARS‐CoV‐2 Test (GenMark, Carlsbad, CA) or Cobas® SARS‐CoV‐2 Test (Roche, Indianapolis, IN). The upper respiratory virus testing was performed on ePlex® Respiratory Pathogen Panel (GenMark)] Samples used: nasopharyngeal swabs 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] healthy controls ‐ not stated (pre‐employment screening in early March 2020; before the first COVID‐19 case was diagnosed in the Lifespan Health System) [3] Other viruses and pathogens ‐ viral respiratory pathogen nucleic acid test [the upper respiratory virus testing was performed on ePlex® Respiratory Pathogen Panel (GenMark)] [4] pre‐pandemic (before January 2020). [2] ‐ [4] The patients whose samples were reactive [positive result on index test] were followed by medical record review to ensure that they did not have COVID‐19. Samples used: Not stated Timing of reference standard: [2] and [3] Not stated (for index test positives, follow‐up history of 17‐38 days from medical records) [4] pre‐pandemic (before January 2020) Blinded to index test: Yes, prior to index test Incorporated index test: No
Flow and timing	Time interval between index and reference tests: Not stated All patients received same reference standard: No Missing data: Not all the samples were available for the four tests (for the Abbott test, 3/1068 healthy samples, 1/105 COVID‐19 samples and 1/119 potential cross‐reactions missing; for SD IgM, 1/119 potential cross‐reactions missing; for SD IgG, 3/119 potential cross‐reactions missing) For sensitivity: 105 of 113 samples were selected to evaluate antibody‐positive rates every 2 days. 8 samples tested in the same 2 days were not used. Out of 8 patients with cross‐reactive results, 2 patients did not have follow‐up history in their medical records. Uninterpretable results: Not stated Indeterminate results: Not stated Unit of analysis: Samples
Comparative
Notes	Funding:The project was funded by Pathology Department of Lifespan Academic Center and Rhode Island Department of Health. Publication status: Pre‐print (not peer reviewed); now published Source: bioRxiv preprint doi: https://doi.org/10.1101/2020.05.29.124776; Journal of Medical Virology Author COI: The authors claimed no conflict of financial interest related to the project.
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?			Unclear
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?	No
Were results presented per patient?	No
Could the patient flow have introduced bias?		High risk