Wellinghausen 2020b.

Study characteristics
Patient Sampling	Purpose: Diagnosis of current convalescent‐phase infection Design: Single‐group study to assess sensitivity [1] Covid patients (n = 137) [1a] Symptomatic outpatients (n = 111) [1b] Asymptomatic, PCR‐confirmed contacts (n = 26) Recruitment: [1] All serum samples sent to our laboratory for SARS‐CoV‐2‐IgG determination between March 24th and May 6th 2020 from outpatients with a positive result of SARS−COV‐2‐RT‐PCR in a nasopharyngeal swab (at least 7 days before serum collection) were considered for analysis (n = 158). Patients with past hospital treatment for COVID‐19 (n = 11) and patients in whom clinical information could not be obtained (n = 10) have been excluded from analysis. Prospective or retrospective: Retrospective Sample size: 137 (137) but 126 (126) included in our review Further detail: Inclusion: [1a] PCR‐positive for SARS‐CoV‐2 in a nasopharyngeal swab (at least 7 days before serum collection) in our laboratory information system (LIS), with clinical symptoms, ambulatory treated patients fulfilling the clinical diagnostic criteria of the Robert‐Koch‐Institute [1b] Asymptomatic Covid contacts with a positive SARS‐CoV‐2‐PCR at least 7 days before serum collection Exclusion: Patients with past hospital treatment for COVID‐19 (n = 11); patients in whom clinical information could not be obtained (n = 10)
Patient characteristics and setting	Setting: [1a] Outpatients or [1b] community All had recovered at the time point of blood collection. Location: MVZ Labor Ravensburg, Ravensburg (private laboratory serving a large number of private practices and hospitals in Southwest Germany as well as most coronavirus test centres in the region) Country: Germany Dates: March 24th to May 6th 2020 Symptoms and severity: [1a] Symptomatic, ambulatory treated [1b] Asymptomatic Demographics: Not stated Exposure history: [1a] Not stated [1b] Contacts of Covid patients Non‐Covid group 1: NA
Index tests	Test name: Anti‐SARS‐CoV‐2‐ELISA IgG Manufacturer: Euroimmun, Luebeck, Germany Antibody: IgG Antigen target: S1‐protein Evaluation setting: Laboratory used in lab Test method: ELISA Timing of samples: All had recovered at the time point of blood collection. [1a] Day 10‐20 pso, n = 11; day 21‐68 pso, n = 100 [1b] Day 9‐20 post‐PCR+, n = 10; day 21‐56 post‐PCR+, n = 16; day 28‐56 post‐PCR+, n = 14 Samples used: Serum Test operator: Lab staff at MVZ Labor Ravensberg Definition of test positivity: Not stated, according to the manufacturer’s instructions Blinding reported: No, no negative group Threshold predefined: Yes, according to manufacturer
Target condition and reference standard(s)	Reference standard: RT‐PCR with the Cobas SARS‐CoV‐2 assay, the AmpliGnost SARS‐CoV‐2 E‐Gen qPCR and the AmpliGnost SARS‐CoV‐2 E‐Gen PCR (PIIM) and AmpliGnost SARS‐CoV‐2 N‐Gen PCR (PIIM), threshold not stated Samples used: Nasopharyngeal swabs Timing of reference standard: Not stated Blinded to index test: Yes, prior Incorporated index test: No Definition of non‐COVID cases: NA Samples used: NA Timing of reference standard: NA Blinded to index test: NA Incorporated index test: NA
Flow and timing	Time interval between index and reference tests: [1a] Not stated [1b] 9‐56 days All patients received same reference standard: Yes Missing data: yes, 11 samples from [1a] with time split 10‐20 days pso excluded from review Uninterpretable results: Not stated Indeterminate results: Equivocal results counted as negative [1a] 10‐20 days pso, one equivocal result. 21‐68 days, three equivocal results Unit of analysis: Patients
Comparative
Notes	Funding: Not stated Publication status: Published paper Source: Journal of Clinical Virology Author COI: No conflicts of interest by all authors
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?	Yes
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?	No
If a threshold was used, was it pre‐specified?	Yes
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?	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?	Yes
Were all patients included in the analysis?	Yes
Did all participants receive a reference standard?	No
Were results presented per patient?	Yes
Could the patient flow have introduced bias?		High risk