Suhandynata 2020a.

Study characteristics
Patient Sampling	Purpose: Diagnosis of acute and convalescent‐phase COVID‐19 Design: Multiple‐group study to estimate sensitivity and specificity: [1] laboratory confirmed COVID‐19 patients (n = 54); [2] patients PCR‐positive on a respiratory panel nucleic acid (RPNA) test for other infections (n = 21), [3] patients with positive for antinuclear antibodies (ANA) or anti‐double stranded DNA (dsDNA) (n = 24) [4] HIV positive patients (n = 10), [5] apparently healthy subjects (no respiratory symptoms per self‐report) (n = 78), [6] pre‐pandemic samples (n = 102) Recruitment: Unclear Prospective or retrospective: Not stated; presume retrospective Sample size: 289 (54) Further detail: No more details available
Patient characteristics and setting	Setting: Mixed; primarily inpatient Location: University of California San Diego Health (UCSD) Country: USA Dates: Not stated Symptoms and severity: Discussion reported 50 (93%) inpatient, and 30/54 (56%) not intubated 'at the time of writing' Demographics: Cases only (calculated from Tab 3): median age 54.5 y (IQR 41, 70.5 y; range 20 to 91 y); 35 (65%) male Exposure history: not stated Non‐Covid group 1: [2] to [4] other conditions or respiratory pathogens (n = 55) Source: Not stated; presume same medical centre Characteristics: not stated Non‐Covid group 2: [5] contemporaneous healthy, [6] pre‐pandemic healthy Source: [5] Not stated, [6] 2018 Characteristics: No further details
Index tests	Test name: [A] DZ‐LITE 2019‐nCoV IgG (CLIA) Assay Kit (Cat # 130219015M) and [B] DZ‐LITE 2019‐ nCoV‐2 IgM (CLIA) Assay Kit (Cat # 130219016M) Manufacturer: Diazyme Antibody: IgM, IgG, IgM or IgG Antigen target: SARS‐CoV‐2 recombinant nucleocapsid (N) and spike (S) proteins Evaluation setting: Laboratory Test method: CLIA Timing of samples: Unclear, data by time were in relation to first positive PCR result Samples used: Serum or plasma, collected in BD Vacutainer collection tubes (K‐EDTA, lithium‐Heparin plasma separator tubes, and/or serum separator tubes) Test operator: not stated Definition of test positivity: ≥ 1.00 AU/mL considered reactive Blinding reported: Unclear Threshold predefined: Yes, as per manufacturer
Target condition and reference standard(s)	Reference standard: Not stated, EUA NAT that had been clinically validated in the laboratory Samples used: not stated Timing of reference standard: First positive PCR was median of 5 days pso (IQR 2.25, 7.75; range 0 to 22 days); data calculated from Tabl 3 Blinded to index test: Not stated; probably Yes Incorporated index test: No Definition of non‐COVID cases: Not stated for group [2] to [5]; group [6] was pre‐pandemic Samples used: Serum or plasma Timing of reference standard: not stated Blinded to index test: Unclear for [2] to [5]; Yes for [6] Incorporated index test: No
Flow and timing	Time interval between index and reference tests: Serum sampling for cases reported by days post‐PCR (Suppl Tabl 3): Day 0 to 7 ‐ 36 (67%), day 8 to 14 ‐ 22 (41%), day >= 15 ‐ 18 (33%) (reported in paper, 19 reported in Table) All patients received same reference standard: No Missing data: None reported Uninterpretable results: None reported Indeterminate results: None reported Unit of analysis: patients
Comparative
Notes	Funding: No funding statement reported Publication status: Published paper Source: Journal of Applied Laboratory Medicine Author COI: No COI statement reported
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?	No
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?			Unclear
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?	No
Were all patients included in the analysis?	No
Did all participants receive a reference standard?	No
Were results presented per patient?	Yes
Could the patient flow have introduced bias?		High risk