Manalac 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] Covid‐19 patients or healthcare workers with RT‐PCR‐confirmed and/or clinical assessment indicated SARS‐CoV‐2 infections (n = 97) [2] Non‐COVID samples (n = 1062) [2a] Concurrent, negative controls with no RT‐PCR results nor clinical assessment indicating SARS‐CoV‐2 infections (n = 137), [Excluded as no reference standard] [2b] Concurrent cross‐reactivity panel with positive serology test results of other infectious diseases or autoimmunity (n = 78) [2c] Pre‐pandemic samples with other diseases (n = 847) No relevant test accuracy results reported for group [2a] Recruitment: Not stated Prospective or retrospective: [1], [2a] and [2b] Unclear [2c] Retrospective Sample size: 1159 (97) of which 956 (31) were eligible for our review Further detail: [1] Specimens from patients or healthcare workers with RT‐PCR‐confirmed and/or clinical assessment indicated SARS‐CoV‐2 infections; [2a] Samples with no RT‐PCR results nor clinical assessment indicating SARS‐CoV‐2 infection; [2b] Samples with positive ANA (by ELISA), dsDNA, RF, cyclic‐citrullinated peptide IgG, RPR, and positive serology for HAV (IgG), HBV (HBV surface Ab, HBV core Ab), HCV, CMV, VZV, EBV, rubella, rubeola, mumps, HSV, and treponema pallidum, all of which were collected during the current COVID‐19 pandemic; [2c] Local patient populations seeking clinical care for rheumatoid diseases, thyroid cancer, and therapeutic drug monitoring. Remnant serum samples from rheumatoid disease screening (n = 643; 2011–2013), therapeutic drug monitoring (TDM) of lamotrigine, levetiracetam, testing for thyroglobulin (Tg), CA125, CA19‐9, CEA, AFP, and CA15‐3 (n = 94; before October 2019), and serum protein electrophoresis test (n = 110; 2012)
Patient characteristics and setting	Setting: Not stated (Covid‐19 patients or healthcare workers; our sample selection consisted of samples collected late in the disease course, mostly during follow up visits) Location: Not stated (Stanford Health Care?) Country: USA Dates: Not stated Symptoms and severity: Not stated Demographics: Not stated Exposure history: Not stated Non‐Covid group 1: [2b] Concurrent other diseases Source: Source not stated, collected during the current COVID‐19 pandemic Characteristics: positive ANA by ELISA (n = 5), dsDNA (n = 5), RF (n = 3), cyclic‐citrullinated peptide IgG (n = 2), and positive serology for HAV (n = 6), HBV (n = 11), HCV (n = 3), CMV (n = 2), VZV (n = 7), EBV (n = 6), rubella (n = 5), rubeola (n = 4), mumps (n = 2), HSV (n = 7), RPR (n = 5), and treponema pallidum (n = 5) Non‐Covid group 2: [2c] Pre‐pandemic, other diseases Source: Local patient populations seeking clinical care for rheumatoid diseases, thyroid cancer, and therapeutic drug monitoring Remnant serum samples from rheumatoid disease screening (n = 643; 2011–2013), therapeutic drug monitoring (TDM) of lamotrigine, levetiracetam, testing for thyroglobulin (Tg), CA125, CA19‐9, CEA, AFP, and CA15‐3 (n = 94; before October 2019), and serum protein electrophoresis test (n = 110; 2012) Characteristics: Samples were from patients ranged in age from 1 to 95 y with 67% female and 33% male A total of 165 samples were positive for one or more of ANA screening by ELISA or specific autoantibody results, with a positive rate of 25%. The samples with Tg results had 23% positive rate for the concurrent anti‐Tg autoantibodies.
Index tests	Test name: [A] Abbott Architect anti‐SARS‐CoV‐2 CMIA IgG [B] Euroimmun anti‐SARS‐CoV‐2 ELISA IgG assay Manufacturer: [A] Abbott; [B] Euroimmun Antibody: [A] IgG; [B] IgG Antigen target: [A] N‐protein; [B] S1 domain of viral spike‐protein Evaluation setting: Laboratory tests performed in lab Test method: [A] chemiluminescent microparticle immunoassay (CMIA); [B] ELISA Timing of samples: 14‐21 days pso: n = 4; > 21 days pso: n = 27; Unknown: n = 66 <= 10 days post‐PCR+: n = 8 > 10 days post‐PCR+: n = 48 Unknown: n = 41 Samples used: Abstract specified "Plasma" [2c] Remnant serum Test operator: Not stated Definition of test positivity: [A] The assay relies on an assay‐specific calibrator to report a ratio of specimen absorbance to calibrator absorbance. The interpretation of result is determined by an index (S/C) value, which is a ratio over the; threshold value. The Abbott IgG assay result is positive (index ≥ 1.4) or negative (index < 1.4). [B] The EI IgG or IgA assay result is positive (index ≥ 1.1), borderline (index ≥ 0.8 but < 1.1), or negative (index < 0.8). Blinding reported: Not stated Threshold predefined: [A]‐[C] by following manufacturer’s instructions
Target condition and reference standard(s)	Reference standard: [1] RT‐PCR‐confirmed and/or clinical assessment indicated SARS‐CoV‐2 infections, threshold not stated; clinical criteria not stated Samples used: [1] nasopharyngeal swab Timing of reference standard: Not stated Blinded to index test: yes, prior to index test Incorporated index test: no Definition of non‐COVID cases: [2b] Concurrent, not tested [2c] Pre‐pandemic Samples used: None Timing of reference standard: [2b] Untested [2c] 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: Not stated All patients received same reference standard: no Missing data: Not stated Uninterpretable results: Not stated Indeterminate results: yes, borderline results for [B] (see Table 3) [B] 35/847 controls borderline [1] No borderline result Unit of analysis: [1] Patients [2] Not stated, possibly patients
Comparative
Notes	Funding: Not stated Publication status: Published paper Source: Clinica Chimica Acta 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?	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?			Unclear
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?	Unclear
Could the patient flow have introduced bias?		High risk