[Evaluation of the Rapid Antigen Detection Kit with the Polymerase Chain Reaction for Detection of SARS-CoV-2 in Respiratory Samples].

The disease caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was named as coronavirus disease-2019 (COVID-19) by the World Health Organization (WHO) in February 11, 2020. The rapid diagnosis of COVID-19 patients is essential to reduce the disease spread. The reverse-transcription polymerase chain reaction (RT-PCR) is the gold standard test to diagnose SARS-CoV-2 acute infection. The rapid antigen test which can detect the presence of viral protein antigens in respiratory tract samples is being investigated as an alternative option, especially in cases where RT-PCR is not available or the test capacity is exceeded, due to its faster results, ease of application, low cost and lack of special equipment and personnel. In this study, it was aimed to evaluate the performance of a commercial rapid antigen test using nasopharyngeal samples of COVID-19 patients confirmed with RT-PCR. From the first day of the research, the first 80 consecutively SARS-CoV-2 RT-PCR positive and 40 RT-PCR negative respiratory samples sent to the Medical Microbiology Laboratory for routine SARS-CoV-2 RT-PCR testing were included in the study. RT-PCR tests of the samples were performed in routine studies with the BioSpeedy SARS-CoV-2 RT-PCR kit (Bioeksen, Turkey). Rapid antigen tests were performed with the Wesail COVID-19 antigen test kit (Guangdong, China) simultaneously with RT-PCR tests. Amongst the 80 positive RT-PCR samples, 56 were detected by the rapid antigen test. All the samples detected as positive with the rapid antigen tests were also positive with RT-PCR. There was a moderate agreement between the qualitative results of both tests (Kappa= 0.609, p<0.001). According to the PCR test, the sensitivity, specificity, positive predictive value (PPV), negative predictive value, and accuracy of the rapid antigen test were; 70%, 100%, 100%, 62.5%, and 80% (96/120), respectively. The sensitivities of the rapid antigen test were calculated as 92.6% in 54 samples with a cycle threshold (Ct) value of <17, 88.7% in 62 samples with a Ct value of <20, 77.8% in 72 samples with a Ct value of <22, and 74.7% in 75 samples with a Ct value of <25. According to our study data; the rapid antigen test was found less sensitive than the RT-PCR test. Negative results obtained with rapid antigen testing cannot exclude SARS-CoV-2 infection and must be confirmed by RT-PCR. In addition, according to the ROC analysis of rapid antigen test positivity obtained according to RT-PCR Ct values, the clinical performance of the rapid antigen test is good in samples with Ct values <20. The rapid antigen test should be evaluated as a reliable screening test in patients with high viral load. To the best of our knowledge, there is no other study in the literature performed with the Wesail COVID-19 rapid antigen test kit (Guangdong, China) used in our study. The fact that PPV was found to be 100% even at a low prevalence period of the pandemic will enable positive patients to be screened quickly and effectively with rapid antigen tests in the first step during the high prevalence period of the pandemic. In the light of these data and our results, it can be predicted that using the rapid antigen test as a screening test in the first step and confirming only negative patients with RT-PCR will contribute to the effective management of the pandemic process in terms of both time and cost. As a result of the study, the rapid antigen test with low sensitivity but high PPD can be included as a facilitating test in the first step of the diagnostic algorithm in terms of rapid identification of the patients with high viral load, initiation of treatment and providing filiation.