ABSTRACT
Antigen tests for severe acute respiratory coronavirus 2 sometimes show positive lines earlier than their specified read time, although the implication of getting the results at earlier time is not well understood. This study aimed to evaluate the clinical utility of an antigen test by evaluating the time period to get positive results and by comparing the test sensitivity with that of a digital immunoassay (DIA) test. We prospectively collected additional nasopharyngeal samples from patients who had already tested positive for SARS-CoV-2 by reverse transcription PCR. The additional swab was used for an antigen test, QuickNavi-COVID19 Ag, and the time periods to get positive results were measured. The sensitivity of QuickNavi-COVID19 Ag was also compared with that of a DIA. In 84 of 96 (87.5%) analyzed cases, the results of QuickNavi-COVID19 Ag were positive. The time to obtain positive results was 15.0 seconds in median (inter quartile range: 12.0-33.3, range 11-736), and was extended in samples with higher cycle thresholds (Ct) (p<0.001). Positive lines appeared within a minute in 85.7% of cases and within 5 minutes in 96.4%. The sensitivities of QuickNavi-COVID19 Ag and the DIA were 87.5% (95% confident interval [CI]: 79.2%-93.4%) and 88.6% (95%CI: 75.4%- 96.2%), respectively. Their results were concordant in 90.9% of cases, with discrepancies present only in cases with Ct values >32. QuickNavi-COVID19 Ag immediately showed positive results in most cases, and the time to a positive reaction may have indicated the viral load. In addition, the sensitivity of the test was comparable to the DIA.
ABSTRACT
BackgroundMolecular tests are the mainstay for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, their accessibility can be limited by the long examination time and inability to evaluate multiple samples at once. This study evaluated the analytical performance of the newly developed rapid molecular assays GENECUBE(R) HQ SARS-CoV-2 and the GENECUBE(R) FLU A/B. MethodThis prospective study was conducted between December 14, 2020, and January 9, 2021, at a polymerase chain reaction (PCR) center. Samples were collected from the nasopharynx with flocked swabs. Molecular tests were performed with the GENECUBE(R) system and reference reverse transcription (RT)-PCR, and the results of the two assays were compared. ResultAmong 1065 samples, 81 (7.6%) were positive for SARS-CoV-2 on the reference RT-PCR. Three showed discordance between GENECUBE(R) HQ SARS-CoV-2 and the reference RT-PCR; the total, positive and negative samples of concordance for the two assays were 99.7%, 100%, and 99.7%, respectively. All discordant cases were positive for GENECUBE(R) HQ SARS-CoV-2 and negative for the reference RT-PCR. SARS-CoV-2 was detected from all three samples by another molecular assay for SARS-CoV-2. For the GENECUBE(R) FLU A/B, the total, positive and negative samples of concordance for the two assays were 99.5%, 100%, and 99.1%. ConclusionThe GENECUBE(R) HQ SARS-CoV-2 and GENECUBE(R) FLU A/B demonstrated sufficient analytical performance to detect SARS-CoV-2 and influenza virus A/B. Key pointsWe prospectively evaluated the analytical performance of the newly developed rapid molecular assays GENECUBE(R) HQ SARS-CoV-2 and the GENECUBE(R) FLU A/B. The two assays showed >99% concordance rate compared with a reference PCR, which indicated their sufficient analytical performance to detect SARS-CoV-2 and influenza virus A/B.
