ESTIMATING SENSITIVITY AND SPECIFICITY OF COVID-19 ANTIBODIES ASSAY POST RT-PCR TESTING

Abstract

Objective: To determine sensitivity and specificity of Roche Sars-cov-2 antibodies assay using real time polymarase chain reaction (RT-PCR) Covid-19 as standard in Pakistani population. Methodology: It was a cross-sectional study conducted in Rehman Medical Institute Peshawar from 1st January 2021 till 15th February 2021. This study include 192 suspected Covid-19 patients. Serum samples set consisted of 122 symptomatic RT-PCR positive patients and 70 negative RT-PCR were used for qualitative detection of Antibodies (CoVID-19 IgG, IgM). Overall and period wise (Post RT-PCR) diagnostic accuracy was determined by comparing results of antibodies assay to Rt-PCR. Chi square test was applied to assess the correlation between post-PCR duration and Anti-SARS-Cov-2. A p-value of ≤0.05 was considered significant. Results: On post-PCR duration and Anti-SARS-Cov-2 analysis, it was evident that the sensitivity of detection increased steadily with increase in duration after viral detection reaching a value of 94.5% after 20 days. Overall sensitivity was 86.9% with PPV of 97.3%. There was a significant level (X2= 6.846, p =.033) of correlation between detection probability of Antibodies and post-PCR duration at 95% Cl. Anti-SARS-Cov-2 showed a specificity of 95.7% and a NPV of 81.7%. Conclusion: Our study demonstrated that in middle and later stages of disease antibodies to SARS-CoV-2 can be detected. This testing strategy can be utilized complementary to molecular based testing of CoVID-19 diagnosis. Also, this can help in determining the seroprevalence of CoVID-19 in community.