Phipps 2020.

Study characteristics
Patient Sampling	Purpose: Diagnosis of acute and convalescent‐phase infection; and assessment of analytical specificity (cross‐reactivity) Design: Multi‐group study, including: [1] Single group of suspected COVID‐19 cases with available prior or same‐day PCR swab test result (n = 173) Excluded from current review: additional groups included to assess analytical specificity: [2] Healthy blood donors (n = 656, 240 pre‐pandemic and 416 from 2020) [3] Patients with SLE (n = 29) [4] Patients with rheumatoid arthritis (n = 20) [5] Patients with previous positive respiratory viral PCR panel (n = 90) Recruitment: Unclear Prospective or retrospective: Retrospective (data collection based on chart review) Sample size: 173 (76) 795 additional non‐COVID‐19 samples excluded from current review Further detail: No more details available
Patient characteristics and setting	Setting: [1] Hospital inpatient Location: Not stated; author's institution University of Texas Southwestern Medical Center, Dallas Country: USA Dates: not stated Symptoms and severity: Unclear; both severe (requiring ICU) and mild/moderate cases included but n per group was not reported and data points reported in Figures did not sum to 76 cases Demographics: not stated Exposure history: not stated
Index tests	Test name: [A] SARS‐CoV‐2 IgG (Abbott 06R86) testing Second in‐house laboratory test reported (ineligible for this review) [B] SARS‐CoV‐2 IgM testing using a laboratory developed protein microarray Manufacturer: [A] Abbott Antibody: IgM or IgG Antigen target: SARS‐CoV‐2 nucleocapsid protein Evaluation setting: Laboratory Test method: [A] chemiluminescent microparticle immunoassay (CMIA) Timing of samples: Fig 3 showed samples collected between day 0 and day c45 Samples used: Plasma Test operator: not stated Definition of test positivity: [A] relative light units (RLU) positive at 1.4 or greater Blinding reported: Unclear; PCR same day or day before Threshold predefined: Yes, as per manufacturer
Target condition and reference standard(s)	Reference standard: [1] RT‐PCR; m2000 Abbott RealTime SARS Cov‐2 assay or [2] isothermal PCR; Abbott ID NOW COVID‐19 assay Samples used: nasopharyngeal swab Timing of reference standard: As for index test, samples collected between day 0 and day c45 Blinded to index test: not stated Incorporated index test: No Definition of non‐COVID cases: As above; single negative for absence of disease Samples used: not stated Timing of reference standard: not stated Blinded to index test: not stated Incorporated index test: unclear
Flow and timing	Time interval between index and reference tests: swab for PCR was same day or prior day All patients received same reference standard: No; isothermal or RT‐PCR (n not stated) Missing data: None reported Uninterpretable results: None reported Indeterminate results: None reported Unit of analysis: patients
Comparative
Notes	Funding: No external funding was received. Publication status: pre‐print Source: medRxiv Author COI: The authors have declared no competing 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?	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?			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?	Unclear
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?	Unclear
Did all participants receive a reference standard?	Yes
Were results presented per patient?	Yes
Could the patient flow have introduced bias?		High risk