Khanna, MBasil, MVManocha, NAgarwal, NChauhan, VArora, RGuleria, AKumar, CChoudhary, JSingh, AShrivastava, KGoel, NSpalgais, SMrigpuri, PKumar, R.2023-08-092023-08-092022-09Khanna M, Basil MV, Manocha N, Agarwal N, Chauhan V, Arora R, Guleria A, Kumar C, Choudhary J, Singh A, Shrivastava K, Goel N, Spalgais S, Mrigpuri P, Kumar R.. Viral Load-based Evaluation of the Sensitivity of Antigen-based Rapid Detection Assay for SARS-CoV-2 . Indian Journal of Chest Diseases & Allied Sciences. 2022 Sep; 64(3): 196-1980377-9343http://imsear.searo.who.int/handle/123456789/221822Background: Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has become a global public health problem. The real-time reverse transcription-polymerase chain reaction (RT-PCR) is the gold standard test for the detection of SARS-CoV-2. However, the assay requires hours to get the final results. Therefore, antigen-based rapid assays are being used extensively to reduce the time. We have evaluated the performance of the antigen-based rapid test for the detection of SARS-CoV-2 virus in comparison with RT-PCR. Materials and methods: Nasopharyngeal and throat swabs were collected from 366 suspected patients of COVID-19 visiting our institute and subjected to qualitative RT-PCR and antigen-based rapid assays to detect the presence of SARS-CoV-2 virus. The sensitivity and specificity of the antigen-based assay were calculated in comparison with RT-PCR. Results: Compared with RT-PCR, sensitivity and specificity of the antigen-based rapid assay were observed to be 70.5% and 98.6%, respectively, in comparison with RT-PCR. However, the sensitivity of antigen-based rapid assay varied significantly with decreasing viral load. The sensitivity of the rapid antigen assay was equivalent to RT-PCR (23/23, 100%) at a higher viral load (Ct value 15�). In contrast, the antigen assay could only detect 3/21 (14.28%) samples with Ct value >30. Conclusion: The antigen-based assay could assist in the rapid screening of a large population. However, the rapid antigen assay might not detect early stages of infection represented by low viral load. Therefore, the antigen-based assay could not replace RT-PCR testing. The study reiterates that all antigen-based negative tests should be confirmed by RT-PCR.Assay sensitivityCOVID-19 pandemicRapid antigen testSARS-CoV-2Viral loadViral surveillanceJournal ArticleIndiaDepartment of Virology Unit, VP Chest Institute, University of Delhi, New Delhi, IndiaDepartment of Microbiology, VP Chest Institute, University of Delhi, New Delhi, IndiaDepartment of Pulmonary Medicine, VP Chest Institute, University of Delhi, New Delhi, India