Seroprevalence of COVID-19 among voluntary blood donors.

Context: COVID-19 usually presents with mild symptoms. No cases of transfusion - transmission of COVID-19 had been reported. Assessing the prevalence of viral infections among blood donors is essential to frame blood safety strategies.

Aim: The main aim of this study is to assess the seroprevalence of SARS-CoV-2 antibodies among healthy and asymptomatic voluntary blood donors by enzyme-linked immunosorbent assay (ELISA).

Setting and design: This cross-sectional study was conducted among voluntary blood donors using a consecutive sampling technique in the Department of Transfusion Medicine, the Tamil Nadu Dr. M.G.R. Medical University, Guindy, Chennai, for 18 months.

Methods: Adhering to COVID-19 pandemic guidelines and donor eligibility criteria, blood samples collected from 500 asymptomatic unvaccinated voluntary blood donors were tested for SARS-CoV-2 (IgG + IgM + IgA and IgG) antibodies by ELISA. Adding IgA to a conventional IgM and IgG serological test improves sensitivity.

Statistical analysis used: The collected donor data were analyzed with IBM SPSS Statistics software. Pearson's Chi-square test and Fisher's exact test were used. P = 0.05 was considered statistically significant.

Results: IgG seropositivity among the donors was 58.8%, and IgM + IgA seropositivity was 29.6%. There was no statistically significant difference in the COVID-19 IgG/IgM + IgA seropositivity status with age, gender, blood group, occupation, or socioeconomic status. The IgG and IgM/IgA/IgG ELISA kits showed a difference of 13 cases which could be attributed to the higher sensitivity of IgG alone ELISA kit. This increased the seroprevalence by 3%.

Conclusion: The majority of donors were either IgG or IgM and IgA positive, despite remaining asymptomatic. The seropositivity rate coincided with the COVID-19 surge among population.