Seroprevalence of COVID-19 among voluntary blood donors

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.

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).

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.

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.

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.

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%.

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.