Schnurra 2020 [A].

Study characteristics
Patient Sampling	Purpose: Diagnosis of current convalescent‐phase infection Design: Single‐group study to estimate sensitivity only [1] Confirmed COVID patients (73 sera from 57 patients) Recruitment: Not stated Prospective or retrospective: Prospective Sample size: 73 (73) samples from 57 (57) patients Further detail: Inclusion: Adult individuals with positive SARS CoV‐2 RNA test after informed consent Exclusion: Ex post, four viral RNA‐positive participants that were asymptomatic and were tested as part of routine screening for healthcare workers or before surgery without contact with infected persons were excluded.
Patient characteristics and setting	Setting: Not stated (none required hospital care, all convalescent) Location: University Clinics and Medical Faculty, University of Leipzig, Leipzig, Germany Country: Germany Dates: Not stated Symptoms and severity: with mild to moderate disease or asymptomatic infection; none was seriously ill or required hospital care. 3 asymptomatic 25 mild (e.g. fatigue, sore throat, headache) 28 moderate (e.g. fever, myalgia, no or mild pneumonia) 1 severe disease (e.g. with dyspnoea, hypoxia, or > 50 percent lung involvement on imaging within 24 to 48 hours) Demographics: Adults Exposure history: Not stated
Index tests	Test name: [A] Roche Elecsys Anti‐SARS‐CoV‐2 [B] Abbott Architect SARS‐CoV‐2 IgG [C] Novatec Novalisa SARS‐CoV‐2 IgG ELISA [D] Virotech SARS‐CoV‐2 IgG ELISA [E] Euroimmun Anti‐SARS‐CoV‐2‐ELISA (IgG) [F] Mediagnost AntiSARS CoV‐2 ELISA [G] Siemens Atellica IM COV2T Manufacturer: [A] Roche [B] Abbott [C] Novatec [D] Virotech [E] Euroimmun [F] Mediagnost [G] Siemens Antibody: [A] IgM, IgG and other Ig antibody bridging [B] IgG [C] IgG [D] IgG [E] IgG [F] IgG [G] IgM, IgG and other Ig antibody bridging Antigen target: [A] N‐protein [B] N‐protein [C] N‐protein [D] N‐protein [E] S1 glycoprotein [F] RBD of S1 glycoprotein [G] RBD of S1 glycoprotein Evaluation setting: All laboratory tests Test method: [A] ECLIA [B] CMIA [C] ELISA [D] ELISA [E] ELISA [F] ELISA [G] Microparticle immunoassay (chemiluminescence?) Timing of samples: Between 2 and 10 weeks after symptom onset or viral RNA testing (additional data provided by author show range from 14 to 70 days post‐PCR test): 2‐3 weeks after PCR+: n = 25 4‐10 weeks after PCR+: n = 48 Sera from symptomatic participants fell into the same groups when classified according to the day of symptom onset. Samples used: Sera were frozen at −20 °C until testing. During the study, serum samples were thawed 1–4 times. Test operator: The tests were performed in three diagnostic routine laboratories and a research laboratory according to the instructions of the manufacturers. Definition of test positivity: [A] Positive ≥ 1 COI, negative < 1 COI [B] Positive ≥ 1.4 index (S/C), negative < 1.4 index (S/C) [C] Positive > 11 NTU, borderline 9–11 NTU, negative < 9 NTU [D] Positive > 11 VE, borderline 9–11 VE, negative < 9 VE [E] Positive ≥ 1.1, borderline ≥ 0.8 to < 1.1, negative < 0.8 [F] Positive > 5 x OD negative control, borderline 3–5 x OD negative control, negative < 3 x OD negative control [G] Positive ≥ 1 index, negative < 1 index Blinding reported: No as only COVID cases included Threshold predefined: yes (all tests performed according to the manufacturer's instructions)
Target condition and reference standard(s)	Reference standard: Positive SARS CoV‐2 RNA test, threshold not stated Samples used: Not stated Timing of reference standard: Not stated Blinded to index test: yes, prior to index test Incorporated index test: no
Flow and timing	Time interval between index and reference tests: 2−3 weeks (N = 25) or > 4 weeks (N = 48) after symptom onset and viral RNA test All patients received same reference standard: yes Missing data: Not stated Uninterpretable results: Not stated Indeterminate results: For calculations, borderline results were considered negative. [C] 8 borderline results [D] 5 borderline results [E] 4 borderline results [F] 15 borderline results Unit of analysis: Samples
Comparative
Notes	Funding: We are also grateful to ... Novatec Immundiagnostica GmbH, Virotech Diagnostics GmbH and Mediagnost GmbH for making their test kits available. The Siemens COV2T tests were provided by Siemens Healthineers and performed by Labor alphaomega, Leipzig. The research did not receive any specific grant from funding agencies. Publication status: Published paper Source: Journal of Clinical Virology Author COI: None.
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?	No
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?	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?	Unclear
Did all participants receive a reference standard?	Yes
Were results presented per patient?	No
Could the patient flow have introduced bias?		High risk