Validation of rapid antigen test as diagnostic tool for detection of SARS-CoV- 2AS compared with real time RT-PCR

Abstract

Introduction: Testing of samples from suspected SARS-COV-2 individuals with rtRT-PCR result leads to delayed in detection of infection. Early recognition of SARS-CoV-2 infection is crucial for both the improvement of turnaround time and limiting the spread of the virus in the Community. Huge number of people affected in pandemic, it is important to use a test that give faster results and can be used on large number of sample. Rapid Antigen Test fulfills both the criteria. AIM: The aim of our study was to evaluate the diagnostic performance of two antigen rapid diagnostic kits (RAT) to diagnose SARS-CoV-2 infection in comparison to rtRT-PCR. So, we evaluated two commercially available antigen kit. Methods: A laboratory based descriptive Crosssectional

study was performed in Trishuli Hospital Nuwakot from January 2021 to December 2021. Result: Out of 1295, 472 tested positive in RAT test while 715 tested positive for SARS-CoV-2 RNA genome via rtRT-PCR. Specificity was 98.2% for Panbio and 96.9% for SD Biosensor. Sensitivity for sample with CT ≤ 20 was 93.5% and 94.2% and for sample with CT ≤ 25 was 93.7% and 93.5% and for CT ≤ 30 was 82.9% and 81.4% with p < 0.001 in case of Panbio and SD Biosensor respectively. The overall diagnostic performance of RAT showed 64.2% sensitivity and 97.8% specificity. Agreement with PCR was excellent for high viral load sample CT<20: Panbio, kappa=0.921; SD Biosensor, Kappa= 0.912 and CT value <25: Panbio, Kappa=0.926; SD Biosensor, Kappa=0.906. Significant difference (p value <0.0001) was observed between RAT+ and RAT- results when compared to CT value obtained from the rtRT-PCR. The diagnostic accuracy for RAT was 79.2% with kappa=0.59 showing moderate agreement and empirical benchmark was set with Youden’s Index 0.597 to be administered as diagnostic purposed. Conclusion: The RAT performed well as a POCT test for early diagnosis of COVID-19 in primary healthcare centers. More crucially finding from our study is that RTPCR proven SARS-CoV-2 infection and negative by RAT are not likely to be infectious.

Keywords: SARS-CoV-2, rtRT-PCR, RAT, Sensitivity, Specificity