Egger 2020 [A].

Study characteristics
Patient Sampling	Purpose: Diagnosis of SARS‐CoV‐2 3‐group study to estimate sensitivity and specificity for diagnosis of active disease Design: [1] confirmed COVID‐19 patients (64 patients, 104 samples) [2] Healthy blood donors (n = 200) and [3] ICU patients (n = 256) Recruitment: [1] Between 15th of March 2020 and 10th of April 2020, of all SARS‐CoV‐2 RT‐PCR (from respiratory specimens) confirmed COVID‐19 patients, that were treated in one of the two tertiary care hospitals, Konventhospital Barmherzige Brueder Linz and Ordensklinikum Linz Barmherzige Schwestern in Linz Austria, blood samples for clinical routine that were sent to central laboratory were included in the present study. [2] Cohorts of 200 consecutive plasma samples from healthy blood donors and [3] 256 consecutive plasma samples of ICU patients from Linz Intensive Care Unit (LICU) study were recruited prior to COVID‐19 outbreak (Dec 3, 2019). Prospective or retrospective: [1] prospective for COVID patients, [2] and [3] retrospective for healthy blood donors/ICU patients Sample size: 520 (64) patients; 560 (104) samples Further detail: Unclear
Patient characteristics and setting	Setting: Inpatients (Konventhospital Barmherzige Brueder Linz and Ordensklinikum Linz Barmherzige Schwestern) Location: Konventhospital Barmherzige Brueder Linz and Ordensklinikum Linz Barmherzige Schwestern, Linz Country: Austria Dates: COVID patients: 15th of March‐10th of April 2020 Symptoms and severity: unclear Demographics: unclear Exposure history: unclear Non‐Covid group 1: [2] Pre‐pandemic healthy blood donors Source: recruited at Red Cross organisation in Linz Austria ‐ 31 Jan‐13 Feb 2008 Characteristics: Cohort of healthy blood donors, 200 consecutive plasma samples that were stored ‐80degrees C and had 1 freeze/thaw cycle Non‐Covid group 2: [3] Pre‐pandemic ICU patients Source: Medical intensive care unit of the Konventhospital Barmherzige Brueder Linz, Austria, recruited from August 9th 2009 to February 8th 2010 Characteristics: Cohort of the Linz Intensive Care Unit (LICU) study; baseline samples of patients admitted to medical ICU of Konventhospital Barmherzige Brueder Linz, Austria, between 9 Aug 2009 and 8 Feb 2010, plasma aliquots store ‐80degrees C and one freeze/thaw cycle
Index tests	Test name: [A] Elecsys Anti‐SARS‐CoV‐2 assay [B] EDI Novel Coronavirus COVID‐19 IgM (reagent lot number P630C) and IgG (reagent lot number P621C) enzyme linked immunosorbent assay Manufacturer: [A] Roche Diagnostics [B] Epitope Diagnostics Inc., San Diego, CA, USA Antibody: [A] IgA, IgM, IgG (total SARS‐CoV‐2 antibody assay [IgA, IgM, and IgG] detecting predominantly, but not exclusively, IgG) [B] IgM or IgG Antigen target: [A] and [B] recombinant nucleocapsid protein (N) Evaluation setting: laboratory Test method: [A] electrochemiluminescence immunoassay (fully automated) [B] ELISA Timing of samples: < 5 days to > 15‐22 days since symptom onset < 5 days pso: 34/104 5‐10 days pso: 35/104 11‐15 days pso: 17/104 16‐22 days pso: 18/104 Samples used: [A] and [B] plasma Test operator: [A] and [B] unclear (seemed to be lab personnel) Definition of test positivity: [A] COI > or = 1.0 positive; COI < 1.0 negative [results were reported as numeric values in form of a cut‐off index (COI; signal sample/cut‐off) as well as in form of a qualitative results non‐reactive (COI < 1.0; negative) and reactive (COI ≥ 1.0; positive]. [B] Single run: If the patient sample optical density (OD) was below the positive cut‐off, the result was reported negative; If the patients sample OD was equal or above the positive cut‐off the patient was reported as positive. Blinding reported: [A] and [B] Not stated Threshold predefined: [A] yes (performed following the manufacturer’s instructions) [B] unclear (did not use the thresholds as reported in the IFU)
Target condition and reference standard(s)	Reference standard: SARS‐CoV‐2 RT‐PCR Samples used: respiratory specimens Timing of reference standard: not reported Blinded to index test: Yes, prior index test Incorporated index test: no Definition of non‐COVID cases: [2] and [3] pre‐pandemic samples Samples used: [2] and [3] NA as pre‐pandemic samples Timing of reference standard: [2] January 31st to February 13th 2008 [3] August 9th 2009 to February 8th 2010 Blinded to index test: yes, done prior index test Incorporated index test: no
Flow and timing	Time interval between index and reference tests: unclear All patients received same reference standard: no Missing data: Not reported Uninterpretable results: Not reported Indeterminate results: Not reported Unit of analysis: samples for COVID patients, patients for healthy blood donors/ICU patients
Comparative
Notes	Funding: Roche Diagnostics provided reagents for Elecsys® Anti‐SARS‐CoV‐2 measurements free of charge. Benjamin Dieplinger and Thomas Mueller have received speaking fees from Roche Diagnostics. Publication status: published Source: Clinica Chimica Acta Author COI: The authors declared that they had no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Yes
Was a case‐control design avoided?	No
Did the study avoid inappropriate exclusions?	Yes
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?	Unclear
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?	Yes
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?		Low 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?	Yes
Did all participants receive a reference standard?	Unclear
Were results presented per patient?	No
Could the patient flow have introduced bias?		High risk