Seroprevalence of anti-SARS-CoV-2 IgG antibodies in admitted patients at a tertiary referral centre in North India

BackgroundSeroprevalence of IgG antibodies against SARS-CoV-2 is an important tool to estimate true burden of infection in a given population. Serosurveys, though being conducted in different parts of India, are not readily published in entirety and often do not report on the different characteristics of the population studied. In this present study, we aimed to serially estimate the seroprevalence of anti-SARS-CoV-2 IgG antibody over 11 months at one of the largest government hospital in India. MethodIn this cross-sectional study which was conducted between between 9th June 2020 and 27th April 2021, consecutive patients admitted to medicine wards or intensive care units, who were negative for SARS-CoV-2 by RT-PCR or CBNAAT were included. The 2linic-demographic features of the subjects were recorded in pre-formed questionnaires. Anti-SARS-CoV2 antibody levels targeting recombinant spike receptor-binding domain (RBD) protein of SARS CoV-2 were estimated in serum sample by the ELISA method. ResultsA total of 916 patients were recruited over 11 months with mean age({+/-}SD) 39.79{+/-}14.9 of years and 55% of population being males. In total 264(28.8%) patients were found to be seropositive. Residency in Delhi and non-smoking status conferred a higher risk for seropositivity. The adjusted odds ratio for seropositivity with regards to no smoking and residence out of Delhi were .31{+/-}.09 (Odds ratio {+/-} S.E) and .65 {+/-} .1 (Odds ratio {+/-} S.E) respectively. No other factors like age, socio-economic status, contact history etc showed significant relationship with seropositivity. ConclusionThe seropositivity rate among hospitalized patients was found to increase with time (from 8.45% to 38%) over a period of 9 months. Residence in Delhi and non-smokers had higher risk for seropositivity on multivariate analysis.