Clinical Performance of the Standard Q COVID-19 Rapid Antigen Test and Simulation of its Real-World Application in Korea

Abstract

The rapid antigen test (RAT) for coronavirus disease (COVID-19) represents a potent diagnostic method in situations of limited molecular testing resources. However, considerable performance variance has been reported with the RAT. We evaluated the clinical performance of Standard Q COVID-19 RAT (SQ-RAT; SD Biosensor, Suwon, Korea), the first RAT approved by the Korean Ministry of Food and Drug Safety. In total, 680 nasopharyngeal swabs previously tested using real-time reverse-transcription PCR (rRT-PCR) were retested using SQ-RAT. The clinical sensitivity of SQ-RAT relative to that of rRT-PCR was 28.7% for all specimens and was 81.4% for specimens with RNA-dependent RNA polymerase gene (RdRp) threshold cycle (Ct) values ≤23.37, which is the limit of detection of SQ-RAT. The specificity was 100%. The clinical sensitivity of SQ-RAT for COVID-19 diagnosis was assessed based on the Ct distribution at diagnosis of 33,294 COVID-19 cases in Korea extracted from the laboratory surveillance system of Korean Society for Laboratory Medicine. The clinical sensitivity of SQ-RAT for COVID-19 diagnosis in the Korean population was 41.8%. Considering the molecular testing capacity in Korea, use of the RAT for COVID-19 diagnosis appears to be limited.

Keywords: Coronavirus disease; Korea; Laboratory surveillance; Rapid antigen test; Real-time reverse-transcription PCR.

Fig. 1

(A) Distribution of RdRp Ct values of all rRT-PCR tests performed on initial upper respiratory tract specimens obtained from newly diagnosed COVID-19 patients in Korea as of December 8, 2020. *Data were collected using the PowerChek 2019 nCoV (Kogene), Allplex 2019-nCoV (Seegene), Standard M nCoV (SD Biosensor), and Real-Q 2019-nCoV (Biosewoom) tests. (B) Clinical sensitivity of SQ-RAT compared with that of rRT-PCR by Ct stratum in specimens. The Ct data were collected using Standard M nCoV. Abbreviations: COVID-19, coronavirus disease; Ct, threshold cycle; LoD, limit of detection; RdRp, RNA-dependent RNA polymerase gene; rRT-PCR, real-time reverse-transcription PCR; SQ-RAT, Standard Q COVID-19 rapid antigen test.