A COVID-19 seroprevalence study undertaken by Jipmer has found that one in every 20 persons in Puducherry showed evidence of the SARS-CoV-2 infection at the end of July.
This is the first serosurvey finding released by Jipmer on Thursday that sheds light on the prevalence of COVID-19 at the community level.
Of the 869 persons tested, 43 had antibodies against the novel coronavirus (4.9%).
The positivity rate for antibodies was higher in city (urban) populations than in rural populations (5.7% against 3.1%). It was higher among women than in men (6.3% in comparison to 3.6%).
The seroprevalence findings showed that the actual prevalence of COVID-19 in the community was about 26 times higher than that detected by Real Time PCR in Puducherry till July.
The results of this study reflect the exposure of people residing in Puducherry to the pathogen as on July 24. The total number of confirmed cases in the district by that date was 2,271, with a cumulative incidence of 0.19% for the population of Union Territory.
The proportion of persons with presence of antibodies in blood was nearly 26-fold (4.9/0.19) larger than that of the cases diagnosed by Real Time PCR tests as on July 24.
“Jipmer already had testing facilities available and we used a test with high levels of sensitivity and specificity that virtually eliminated errors in diagnostic results,” said Rajesh N.G., additional professor and Jipmer spokesman. “Although the density of COVID-19 cases since has increased from cases detected through RT-PCR, we can only hypothesise that the seroprevalence will be higher until we have the data to back it up,” Dr. Rajesh said.
The presence of antibodies was studied using an immunoassay with reported sensitivity of 99.5% and specificity of 99.8% at more than 14 days after exposure to the virus.
Experts from the Departments of Preventive and Social Medicine and Microbiology were involved in the selection of patients and collection of blood samples, conduct of the tests and analysis of the results.
The blood samples were collected from randomly selected adults aged 18 and above from 30 clusters with a ratio of 21 from urban and 9 from rural areas to reflect the population distribution of the Union Territory. The samples were collected between August 11 and 16.
Jipmer proposes to undertake a repeat survey in the second/third week of September to assess the extent of exposure by the last week of August (accounting for the 14-day period for the emergence of immunoglobulin IgG antibodies) and further serial surveys at an appropriate time as the pandemic continues.