Evaluation of Performance of Detection of IgG and IgM Antibody Against Spike Protein of SARS-CoV-2 by a Rapid Kit in a Real-Life Hospital Setting
Abstract Background Antibody testing are often used for serosurveillance of COVID-19. ELISA and Chemiluminesence based antibody test are quiet sensitive and specific for such serological testing. Rapid antibody tests are developed and effectively used for this purpose. But their diagnostic efficiency needs to be evaluated. So, the present study was conducted in a dedicated COVID-19 hospital in Delhi, India to evaluate the diagnostic efficacy of a Rapid antibody kit for COVID-19. Material and Method : Sixty COVID-19 confirmed cases by RT-PCR were recruited and categorized as early, intermediate and late cases based on the number of days of their first RT-PCR + ve tests, 20 subjects in each category. Twenty samples from pre-covid era were taken as controls. IgM and IgG antibodies against RBD of spike protein (S) of SARS-CoV2 virus were detected by Rapid antibody test and compared with total antibody against the nucleocapsid (N) antigen of SARS-CoV-2 by Electrochemiluminescence based Immunoassay (ECLIA). Results The detection IgM against Receptor binding domain (RBD) of spike protein by rapid kit was 0-37.5% sensitive and 0-100% specific for diagnosis of SARS-CoV-2 infection. However, efficacy of detection of IgG by rapid kit was 87–89% sensitive and 75–100% specific when compared with total antibody against N antigen measured by ECLIA based immunoassay. Conclusion It can be concluded that detection of IgM against RBD of S protein by rapid kit is not effective but IgG detection can be used as an effective diagnostic tool for SARS-COV-2 infection.