Alvim 2020.

Study characteristics
Patient Sampling	Purpose: Diagnosis of COVID‐19 current acute‐phase infection and current convalescent‐phase infection Design: This paper describes the validation of an in‐house test. Data were extracted only for the commercially available test. This is a single‐group analysis for sensitivity. [1] Confirmed COVID patients (437 samples) Recruitment: Not stated Prospective or retrospective: [1] Prospectively for samples collected at UFRJ COVID Screening and Diagnostic Center; unclear for samples collected at the State Hematology Institute Hemorio Sample size: 437 (437) Further detail: [1] Only symptomatic subjects who presented at least two of the following symptoms were included: loss of taste or smell, fever, shortness of breath, diarrhoea, headache, extreme tiredness, dry cough, sore throat, runny or stuffy nose, or muscle aches. PCR‐positive individuals who were followed along time
Patient characteristics and setting	Setting: Not stated Location: State Hematology Institute Hemorio and UFRJ COVID Screening and Diagnostic Center, Federal University of Rio de Janeiro (UFRJ) Country: Brazil Dates: Not stated Symptoms and severity: Clinical characteristics of the patients not documented Demographics: Not available Exposure history: Not available Non‐Covid group 1: NA
Index tests	Test name: This paper primarily describes an in‐house assay. Data extraction was only performed for the commercially available test. anti‐SARS‐COV‐2 IgG ELISA (#EI 2606‐9601 G) Manufacturer: Euroimmun Antibody: IgG Antigen target: S1 subunit of the spike‐protein of SARS‐COV‐2 Evaluation setting: Laboratory Test method: ELISA Timing of samples: Samples collected from D0 after symptom onset, up to 98 days after symptom onset 0‐5 days pso: n = 33 6‐10 days pso: n = 42 11‐15 days pso: n = 83 16‐20 days pso: n = 62 21‐25 days pso: n = 56 26‐30 days pso: n = 54 31‐98 days pso: n = 107 Samples used: Unclear Test operator: Not stated Definition of test positivity: Not stated (as per manufacturer's instructions) Blinding reported: Unclear (no as only COVID cases tested) Threshold predefined: As per manufacturer’s instructions
Target condition and reference standard(s)	Reference standard: RT‐PCR, threshold not stated Samples used: Unclear Timing of reference standard: Not stated Blinded to index test: yes, performed prior to index test Incorporated index test: No Definition of non‐COVID cases: NA
Flow and timing	Time interval between index and reference tests: Not stated All patients received same reference standard: Yes Missing data: yes (more data reported in study that are not included in our review, e.g. non‐COVID samples for specificity results) Uninterpretable results: Not stated Indeterminate results: Not stated Unit of analysis: Samples (individuals who had tested positive by PCR and were followed over time)
Comparative
Notes	Funding: This work was supported by Senai CETIQT, Senai DN and CTG, and by the Brazilian research funding agencies Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and Instituto Serrapilheira. DASR was supported by a fellowship from CNPq (DTI‐A; 401209/2020‐2). Publication status: Pre‐print (not peer reviewed) Source: medRxiv Pre‐print Author COI: We declare no competing interests.
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?	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?	No
Could the patient flow have introduced bias?		High risk