Yang 2020 [A].

Study characteristics
Patient Sampling	Purpose: Diagnosis of acute and convalescent‐phase infection Design: Multi‐group study to estimate sensitivity and specificity: [1] patients presenting to ED and displaying signs and symptoms suspicious for COVID 19 (n = 87, only 42 PCR‐confirmed cases providing 120 samples could be included in the review) [2] Pre‐pandemic ED patients (sample number = 320; unclear patient number) [3] Pre‐pandemic healthy blood donors (n = 256) Groups [2] and [3] used for different assays Additional cohorts reported but not extracted for the purposes of this review: [4] convalescent patients who were PCR‐positive or had Covid‐19‐like illness but were not tested, and had been symptom‐free for at least 14 days (n = 145) [5] Cross‐reactivity panel, including: patients treated for recent non‐Covid‐19 respiratory infections (n = 30); patients with antibodies to known microbial agents or with autoantigens (n = 78); patients who tested positive for one of the respiratory viruses in the Respiratory Pathogen PCR Panel (n = 16) Recruitment: Unclear Prospective or retrospective: Retrospective Sample size: 696 (120) Further detail: Not further described
Patient characteristics and setting	Setting: Accident and Emergency; hospital inpatient Location: Wells Cornell Medicine, New York Country: United States Dates: 6th March to 4th April 2020 Symptoms and severity: 14/42 (33%) discharged from ED 28/42 (67%) inpatients 23/42 (55%) required ICU care 24/42 (57%) required intubation Demographics: age: mean 56.5 years, SD 16.0; sex: 33/42 male (79%) Exposure history: Not stated Non‐Covid group 1: [2] Pre‐pandemic ED patients Source: [2] Pre‐pandemic (July 2019) Characteristics: [2] Not stated Non‐Covid group 2: [3] Pre‐pandemic healthy blood donors Source: [3] Pre‐pandemic (before 2019) Characteristics: [3] Not stated
Index tests	Test name: [A] Pylon COVID‐19 IgM and IgG assays; [B] New York SARS‐CoV‐2 MIA Manufacturer: [A] ET Healthcare, Palo Alto, CA, USA [B] Luminex Corporation, Austin, TX, USA (uses recombinant antigen produced at the Wadsworth Center/NYSDOH coupled with a cDNA copy of the N gene of SARS‐CoV; coupling carried out using a purchased kit from Luminex) Antibody: [A] IgG, IgM, IgG or and IgM [B] Total antibody Antigen target: [A] S‐receptor binding domain and recombinant nucleocapsid protein [B] recombinant nucleocapsid protein Evaluation setting: Laboratory Test method: [A] cyclic enhanced fluorescence assay (CEFA) [B] microsphere immunoassay (MIA) Timing of samples: 0 to > 32 days pso, of the 120 samples from 42 PCR+ cases: 8, 7% day 0‐3 33, 28% day 4‐7 42, 35% day 8‐14 15, 13% day 15‐20 21, 18%, day 21‐32 1, 0.8% day > 32 Samples used: Serum Test operator: Not stated Definition of test positivity: [A] Samples with an index value ≥ 1 were designated as positive [B] Samples with an index value ≥ 1.78 were designated as positive Blinding reported: Unclear Threshold predefined: Yes
Target condition and reference standard(s)	Reference standard: RT‐PCR (RealStar SARS CoV‐2 RT‐PCR kit 1.0; Altona Diagnostics USA, Inc) Samples used: Nasopharyngeal swabs Timing of reference standard: Unclear; on presentation at ED Blinded to index test: Unclear; probably yes Incorporated index test: No Definition of non‐COVID cases: [2] and [3] Pre‐pandemic controls [4] [5] unclear [6] PCR+ for other infection Samples used: NA Timing of reference standard: NR Blinded to index test: Yes Incorporated index test: No
Flow and timing	Time interval between index and reference tests: Unclear All patients received same reference standard: No Missing data: Yes, MIA results reported for only 114/120 samples from PCR+ cases; no a‐b data for 45 PCR‐ COVID suspects Uninterpretable results: NR Indeterminate results: NR Unit of analysis: Samples
Comparative
Notes	Funding: Unclear Publication status: Published paper Source: Clinica Chimica Acta Author COI: ZZ received seed instruments and sponsored travel from ET Healthcare. The manufacturers did not review the article and had no input on data analysis prior to the manuscript submission.
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?	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?	Yes
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?		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?	No
Did all participants receive a reference standard?	Yes
Were results presented per patient?	Yes
Could the patient flow have introduced bias?		High risk