Evaluation of diagnostic utility and performance of rapid SARS-CoV- 2 antigen detection assay in comparison with Real-Time RT-PCR in Kolkata, India

Background: COVID-19 has so far affected millions of people in India. The present study was undertaken to find out the performance and reliability of rapid antigen test (RAT) in compared to reverse transcription polymerase chain reaction (RT-PCR).Methods: The pre and existing medical conditions and clinical signs and symptoms were noted. The nasopharyngeal swab samples were taken for RAT, while both nasopharyngeal and oropharyngeal swab samples were mixed in a sterile viral transported medium (VTM) for RT-PCR. All patients were examined by RAT, while symptomatic negative in RAT were re-examined by RT-PCR.Results: Total 18,965 samples were examined by RAT and 3,998 samples by RT-PCR. Among them, only 5,753 patients (30.3%) were symptomatic and 1,757 patients (9.2%) were symptomatic positive. RAT showed overall 15.2% positive cases. Only 3.7% samples exhibited false negative results in RAT, which were found positive in RT-PCR. Interestingly, Ct (cycle threshold) values were >30 in all these samples.Conclusion: Hence, specific antigen-based rapid diagnostic test (RDT) will be most useful and reliable among any other qualitative tests for screening purpose.