DIAGNOSTIC PERFORMANCE OF SARS-CoV-2 BY ANTIGEN DETECTION ENZYME IMMUNOSORBENT ASSAYS

Abstract

Background:Quick identication and isolation ofCOVID-19 casesis criticalin curtailing the pandemic.Rapid immunochromatographic antigen tests (RAT)were introduced forthe same purpose butwere unable to achieve the expected impact on pandemic control because ofitslowsensitivity.Enzyme Linked Immunosorbent Assay (ELISA) is more sensitive than immunochromatography test. Hence, the recently introduced COVID-19-AntigenELISA (J. Mitra & Co. Pvt. Ltd COVID-19 Ag MICROLISA) is believed to be more sensitive than RAT tests available for the rapid diagnosis of COVID-19. Further,COVID-19-Antigen-ELISA(COVID-Ag-ELISA) can also be performed on sample collected inViralTransportMedium(VTM) that has been collected for gold-standard Real-time, Reverse transcriptase polymerase chain reaction (RT-PCR) used for diagnosis of COVID-19. Therefore, the present study was undertaken to assess performance of COVID-A g-ELISA with RAT and gold standard RT-PCR test. Method: This study was done on VTM samples that were collected for RT-PCR test and stored after RT-PCR test results at -80℃ or -20℃. COVID-19-AntigenELISAtest was performed as per kit literature provided by the manufacturer. The sensitivity,specicity, PPV and NPV were calculated to evaluate the performance of ELISA. Result: In thisstudy, percentage positivity of COVID-Ag-ELISAwas higher than RATbut lower than RT-PCR.Also, ELISA was able to pick up 27RATnegative samples. Sensitivity ofELISAforsamples withCt value ≤ 25 (62.5) was almostsimilarto samples withCt value ≥ 25 (64.5). Specicity of test was 100%. In thisstudy, percentage positivity of COVID-Ag-ELISAtest wasfound inversely proportional to duration of storedVTMsamples.Conclusion:COVID-Ag-ELISAcanbeusedas a screeningtest alternative toRAT.