Kaltenbach 2020 [A].

Study characteristics
Patient Sampling	Purpose: Diagnosis of acute and convalescent‐phase COVID‐19 infection Design: Three‐group study to estimate sensitivity and specificity: [1] Symptomatic and post‐symptomatic PCR‐confirmed Covid‐19 patients (n = 341) [2] PCR‐negative symptomatic patients (n = 115) [3] Pre‐pandemic blood donor controls (n = 150) Recruitment: Unclear; stated RT‐PCR‐positive 'committed' to participating (total positive at time of study period was 802), and RT‐PCR‐negative were randomly selected from 4509 negative results Prospective or retrospective: Prospective Sample size: 606 (341) Further detail: No more details available All RT‐PCR‐tested individuals were eligible for participation except when they were < 18 years of age, had a severely compromised immune system, were hospitalised at the time of sample collection, or were deceased.
Patient characteristics and setting	Setting: Community testing facility (hospitalised patients were excluded) Location: Basel‐Landschaft canton; 'Abklarungsstation COVID‐19' in Munchenstein Country: Switzerland Dates: 11th April 2020 to 22nd April 2020 Symptoms and severity: 35 (10%) bedridden during acute disease 62 (18%) required help for their daily activities 244 (72%) had no restrictions on daily activities Demographics: Sex: 177/349 (51%) male) Age: only available with the following breakdown: PCR‐positive <= 7 days (n = 31): median 45 years range 21‐80 years PCR‐positive > 7 days and <= 12 days (n = 46): median 51 years, range 20‐80 years PCR‐positive > 12 days (n = 272): median 51.5 years, range 17‐93 years [Numbers per group did not seem to correlate with accuracy data by time pso e.g. above added to 77 patients at <= 12 days, but Tabl 4 reported only 54 patients at <= 14 days] Exposure history: Not stated Non‐Covid group 1: PCR‐negative Source: Negative cohort from same source as positive patients Characteristics: Sex: 48/111 (43%) male Age: median 48 years, range 19‐87 years Non‐Covid group 2: Pre‐pandemic controls Source: Non‐renumerated blood donors from Swiss cantons of Thurgau, Basel, Bern, Waadt and Geneva, taken on 16th and 17th December 2016 Characteristics: Not stated
Index tests	Test name: [A] Anti‐SARS‐CoV‐2‐ELISA‐IgA (# EI 2606‐9601 A) [B] Anti‐SARS‐CoV‐2‐ELISA‐IgG (# EI 2606‐9601 G) [C] EDI Novel Coronavirus COVID‐19 IgM ELISA kit (# KT‐ 114 1033) [D] EDI Novel Coronavirus COVID‐19 IgG ELISA kit (# KT‐1032) Manufacturer: [A] Euroimmun AG, Lubeck, Germany [B] Euroimmun AG, Lubeck, Germany [C] Epitope Diagnostics, Inc., USA [D] Epitope Diagnostics, Inc., USA Antibody: [A] IgA [B] IgG [C] IgM [D] IgG Antigen target: Unclear Evaluation setting: Laboratory Test method: [A] ELISA [B] ELISA [C] ELISA [D] ELISA Timing of samples: <= 14 days: 54/345 (16%) 15‐20 days: 52/345 (15%) >= 12 days: 239/345 (69%) Samples used: [1] and [2] Serum [3] and [4] Serum and plasma Serum and plasma for all tests (some results in Suppl file) Test operator: Unclear Blood collection was performed by a medical assistant or nurse; samples either transferred to the diagnostic lab or directly processed on site in the make‐shift laboratory Definition of test positivity: [A] and [B] OD ≥ 1.1 xOD of the calibration sample [C and [D] "defined IgG‐ and IgM‐specific cut‐off values relative to the average OD of three negative controls (ODNC) as follows: OD sample ≥ (1.1+x)×ODNC is interpreted as positive" Blinding reported: Unclear Threshold predefined: Yes, as per manufacturer
Target condition and reference standard(s)	Reference standard: RT‐PCR Samples used: Unclear Timing of reference standard: Unclear Blinded to index test: Yes Incorporated index test: No Definition of non‐COVID cases: [2] PCR [3] Pre‐pandemic Samples used: Unclear Timing of reference standard: Unclear Blinded to index test: Yes Incorporated index test: No
Flow and timing	Time interval between index and reference tests: Unclear All patients received same reference standard: Yes Missing data: Nothing mentioned 4 PCR‐negative found to be positive on both Euroimmun IgG and IgA and Epitope Diagnostics (EDI) IgG, considered FN PCR results were excluded. Study further reported variable numbers in each group in different parts of the paper. e.g. 341 patients in group [1] in the methods section, but 349 patients in Tabl 1 and 345 in Tabl 4 e.g. 115 PCR‐negative patients in group [2] in the methods section but 111 in Tabl 1 e.g. total sample size 606 in methods section but 605 in table 3 and 607 in figure 1 Uninterpretable results: None reported Indeterminate results: "All samples with uncertain result were considered negative for the analysis" [A] 27 (15 FN, 12 TN) uncertain results/345 (4%) [B] 14 (12 FN, 2 TN) uncertain results/345 (3%) [C] 37 (35 FN, 2 TN) uncertain results/345 (10%) [D] 23 (16 FN, 7 TN) uncertain results/345 (5%) Unit of analysis: Patients
Comparative
Notes	Funding: This study was sponsored by Jurg Sommer, head of the "Amt fur Gesundheit". FR is funded by the NCCR 'Molecular Systems Engineering'. Funding for JD from the two Cantons of Basel through project grant [X] granted by the ETH Zurich is acknowledged. Publication status: Pre‐print (not peer reviewed) Source: medRxiv Author COI: Nothing 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?	No
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?	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?			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?	No
Did all participants receive a reference standard?	Yes
Were results presented per patient?	Yes
Could the patient flow have introduced bias?		High risk