Ng 2020 [A].

Study characteristics
Patient Sampling	Purpose: Diagnosis of acute and convalescent‐phase infection, and to evaluate immune response kinetics and seroprevalence Design: Multi‐group study estimating sensitivity and specificity (possible that [1] and [2] could be considered as a single group, but recruitment was not sufficiently clearly described) [1] RT‐PCR‐confirmed COVID‐19 cases (n = 43 patients) [2]: SARS‐CoV‐2 PCR‐negative UCSF patients (indication for PCR testing was not reported but implied COVID‐19 suspects?) (n = 163 patients for test [A] and 39 patients for test [B]) [3]: Pre‐pandemic controls collected by Abbott Laboratories (US blood donors) (n = 1013 for test [A], n = 1492 for test [B]) Two additional cohorts evaluated for seroprevalence survey not extracted for this review, including [4] patients hospitalised for indications other than COVID‐19 respiratory disease (March‐April 2020) (n = 387, and [5] contemporaneous blood donors (n = 1000) Recruitment: Unclear Prospective or retrospective: Not explicitly stated but likely retrospective Sample size: Covid suspects: 206 (43) for test A and 79 (42) for test B All patients: 1219 (43) for test [A]; 1574 (43) for test [B] Total samples: 1671 for test [A], 1877 for test [B] Further detail: No more details available
Patient characteristics and setting	Setting: Mixed (outpatient and inpatient) Location: University of California, San Francisco (UCSF) Medical Center and the San Francisco Veterans Affairs (SFVA) Health Care System Country: United States Dates: March‐April 2020 Symptoms and severity: 2 (5%) asymptomatic; 38 (88%) >= 1 symptom (primarily cough, fever, shortness of breath); 3/43 (7%) info not available Severity: 15 (35%) reportedly admitted to ICU, however data by severity exceeded the total number of patients Demographics: 28 (65%) male; mean age 59 yrs (SD 18) Exposure history: Not stated Non‐Covid group 1: Group [2]: SARS‐CoV‐2 PCR‐negative UCSF patients Source: March‐April 2020 at UCSF Medical Center Characteristics: Not stated Non‐Covid group 2: Group [3]: Pre‐pandemic controls (US blood donors) Source: Samples collected by Abbott Labs before the COVID‐19 pandemic (no more details available) Characteristics: Not stated
Index tests	Test name: [A] Architect SARS‐CoV‐2 IgG assay [B] Architect SARS‐CoV‐2 IgM assay (reported as prototype; not currently commercially available) Manufacturer: Both Abbott Laboratories Antibody: [A] IgG [B] IgM Antigen target: [A] N‐protein [B] S‐protein Evaluation setting: Both Laboratory Test method: CLIA Timing of samples: day 1 to at least day 49 pso (Fig 2 D and E) [A] n samples by days pso: 41 (10%) day 1‐7 (from 16 patients); 106 (25%) day 8‐14 (from 24 patients); 113 (27%) day 15‐21 (from 21 patients); 163 (38%) day 22+ (up to 49) (from 18 patients) [B]: 26/346 (8%) day 1‐7 pso; 91/346 (26%) day 8‐14 pso; 83/346 (24%) day 15‐21 pso; 146/346 (42%) day 22+ pso Samples used: Serum, plasma Test operator: Not stated Definition of test positivity: Methods implied per manufacturer (i.e. IgG positive if Index S/C >= 1.4; IgM S/C >= 0.6) Blinding reported: Not stated Threshold predefined: Yes, as per manufacturer
Target condition and reference standard(s)	Reference standard: RT‐PCR test (no more details available) Samples used: NP and/or OP Timing of reference standard: Not stated Blinded to index test: Yes (done earlier) Incorporated index test: No Definition of non‐COVID cases: Group [2]: RT‐PCR (no more details available) Group [3]: Pre‐pandemic Samples used: Group [2]: NP and/or OP Group [3]: NA Timing of reference standard: Not stated Blinded to index test: Yes (done earlier) Incorporated index test: No
Flow and timing	Time interval between index and reference tests: Not stated All patients received same reference standard: Yes (if we only included group [2], as we considered any RT‐PCR to be ok and 'the same', although that is a bit of a stretch); or, No if we included pre‐pandemic samples from group [3] Missing data: None reported Uninterpretable results: None reported Indeterminate results: None reported Unit of analysis: Patients and samples [Fig 1 D and E gives per pt data for cases]
Comparative
Notes	Funding: This work was funded by multiple NIH grants and in part by Abbott Laboratories. Funders had no role in the study design, writing the manuscript, or decision to publish. However, employees from Abbott Labs contributed to sample collection, IgG and IgM testing, and data analysis. Publication status: Pre‐print article Source: Pre‐print server (medXriv) Author COI: One author is the director of the UCSF‐Abbott Viral Diagnostics and Discovery Center (VDDC) and receives research support funding from Abbott Laboratories. Five other authors are employees of Abbott Laboratories.
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?	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?	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?	Yes
Were results presented per patient?	No
Could the patient flow have introduced bias?		High risk