COVID-19 testing with RT-PCR may result in late detection of disease. Rapid Antigen Detection Test is much faster, easy to perform and suitable for population wise testing strategies. Our study assesses the diagnostic accuracy of Rapid Antigen Test (RAT) compared to RT-PCR in peripheral health care set up. The study was aimed to detect the diagnostic accuracy of the COVID-19 antigen test such as to understand its position as a point of care device in a resource poor clinical set up during a rapidly spreading and high mortality ridden pandemic. In this study we compared SARS-CoV2 rapid antigen test and RT-PCR by considering that RT-PCR is the gold standard test in a rapidly arranged molecular diagnostic lab. We analyzed total 389 samples who have undergone both rapid antigen test and RT-PCR. The correlation between Ct values in RT-PCR test and RAT positivity was analyzed. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy were found to be 75.47% (61.72-86.24%), 92.26% (88.87-94.88%), 33.92% (25.60-43.36%), 98.62% (97.8-99.14%) and 91.42% (88.19-94.19%), respectively. The k-coefficient of agreement between RAT and RTPCR was 0.615 ± 0.056 (0.504-0.724). For specimens with Ct value < 20, 20-25, 26-30, 30-35 and >35 were 100%, 90.3%, 80.3%, 60% for Ct value and 25% respectively. Our results suggest that RAT may be considered as an alternative to RT-PCR testing in peripheral health care set up. We reveal the importance of implementing rapid antigen test properly combined with clinical assessment of symptomatic patients so that it can be used in primary health care where RT-PCR testing facility is not available.
Key words: COVID-19, Ct value, Point of Care diagnostic test, Rapid Antigen Test, RT-PCR, SARS-CoV-2
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