A-372 Increased Sensitivity in Detection of SARS-CoV-2 Antigen Using RADI COVID-19 Ag Rapid Test

Abstract

Abstract Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) rapid point-of-care antigen tests can provide easy and fast results for the diagnosis of coronavirus disease 2019 (COVID-19). However, due to the lower sensitivity of rapid antigen tests relative to reverse transcription polymerase chain reaction (RT-PCR), they might miss many infectious COVID-19 cases. We evaluated and compared a new rapid antigen test with the current approved one. Methods The RADI COVID-19 Ag Rapid Test (KH Medical, Hanam, Korea) was validated with a total of 1054 pre-confirmed residual nasopharyngeal swab samples (258 positives and 796 negatives) by PowerChek 2019-nCoV Real-time PCR (Kogene Biotech, Seoul, Korea). Among them, 258 positives and 546 negatives were used to compare the RADI COVID-19 Ag Rapid Test with the STANDARD Q COVID-19 Ag Test (SD Biosensor, Suwon, Korea). Results Using RT-PCR results as the reference, the overall sensitivity and specificity of RADI COVID-19 Ag Rapid Test were 82.2% (212/258; 95% confidence interval, CI [76.9–86.6]) and 99.1% (789/796; 95% CI [98.2–99.7]), respectively. The positive predictive value and negative predictive value were 96.8% (212/219; 95% CI [93.5–98.5]) and 94.5% (789/835; 95% CI [93.0–95.7]), respectively. The accuracy was 95.0% (1001/1054; 95% CI [93.5–96.2]) with Cohen's kappa value of 0.86 (95% CI [0.82–0.89]). The positive percent agreement and negative percent agreement of the RADI COVID-19 Ag Rapid Test for STANDARD Q COVID-19 Ag Test were 97.0% (159/164; 95% CI [93.0–99.0]) and 90.6% (580/640; 95% CI [88.1–92.8]), respectively, and those of STANDARD™ Q COVID-19 Ag Test for RADI COVID-19 Ag Rapid Test were 72.6% (159/219; 95% CI [66.2–78.4] and 99.2% (580/585; 95% CI [98.0–99.7], respectively. The overall percent agreement between the two rapid antigen assays was 91.9% (739/804; 95% CI [89.8–93.7]) with Cohen's kappa value of 0.78 (95% CI [0.73–0.83]). Among the 65 discrepant samples between the two rapid antigen assays, 56 were positive as per RT-PCR, which showed 53 samples negative for STANDARD Q COVID-19 Ag Test and 3 samples negative for RADI COVID-19 Ag Rapid Test. The median E gene Ct value of the 65 discrepant samples was 28.2 (interquartile range: 26.1–32.3). Conclusion RADI COVID-19 Ag Rapid Test provides acceptable sensitivity and specificity according to the validation criteria for KFDA immunological test product approval. Furthermore, RADI COVID-19 Ag Rapid Test shows improved sensitivity compared to the current approved rapid antigen test.