Publication:

Seroprevalence of SARS CoV 2 specific Ig G antibodies in District Srinagar, Kashmir: a population based study

Background The seroprevalence studies are conducted with the aim of estimating the extent of SARS CoV2 infection in any community. A cross sectional population based study was conducted in Srinagar district of Kashmir, India so as to provide relevant information on the proportion of people who have experienced a recent or past infection.

Methods An estimated sample size of 2400 was calculated based on anticipated seroprevalence of 20% and an absolute error of 2.5%. 20 clusters were selected using 2 stage cluster sampling. A set of questions on a mobile based application i.e Epicollect 5 was used to collect information on various variables and 3-5 ml of venous blood was taken for Ig G antibody testing. Chemiluminiscent Microparticle Immunoassay (CMIA) procedure using fully automated analyser by Abbott with sensitivity of 100% and specificity of 99.6% was used to detect IgG antibodies against SARS COVID-2.

Results 2480 eligible individuals participated in the study. The overall seroprevalence of Ig G antibodies against SARS-CoV 2 in the current study was 40.6% (95% CI 38.7-42.6), with seroprevalence being significantly higher among females (44.7% as compared to 37.5%).  Age standardized seroprevalence revealed that seroprevalence increased with the increasing age.

Conclusions The findings of Seroprevalence study may fail to reveal the true picture of covid-19 infection as there were certain participants who were positive for COVID on RTPCR but were IgG negative. Thus, the individual variation of immune response to the virus, role of mucosal Ig A antibodies and T cell mediated immunity cannot be ruled out.