Evaluation of the currently used antigen-based Rapid Diagnostic Test for the detection of SARS CoV-2 virus in respiratory specimens

ABSTRACT

Background:COVID-19 is a respiratory disease caused by novel coronavirus SARS CoV -2 and has been declared as pan- demic by WHO. The timely detection of cases and their contacts is crucial to help curtail the pandemic. Introduction of antigen based RDT has been able to bridge the time gap of detection and tracing as these tests are timely and easy to perform. However the real world performance of these assays is uncertain and the sensitivity of the test is claimed to be between 50% to 87%. This study was conducted to evaluate the currently used antigen -based RDT for the detection of SARS CoV-2 virus in respiratory specimens. Methods:This prospective study included patients who were seeking healthcare in Ophthalmology department for eye ailments and were subjected to SARS CoV-2 antigen based RDT. Regardless of results of RDT, nasopharyngeal swabs were collected from these patients and were tested for SARS CoV-2 RNA by real-time RT PCR using commercial assay (SD Biosensor). The evaluation of antigen-based RDT for the detection of SARS CoV-2 virus was performed with real time RT-PCR as gold standard. Results:A total of 564 patients were tested by both antigen based RDT and real time RT -PCR. The antigen based RDT exhibited analytical sensitivity and specificity of 37.5% and 99.79% respectively. Positive predictive value and negative predictive value of RDT were 96.4% and 91.6% respectively. Negative correlation was found between antigens based RDT’s positivity and Ct values of E and RdRp genes. Conclusions:Overall poor sensitivity of RDT does not allow adopting it as point of care test in screening for COVID -19 and it only serves as an additional test to RT-PCR because of potential false negative results.