Seroprevalence of COVID-19 infection among attendees in graduation ceremony of 11 Northeastern Rajabhat universities: evaluation of rapid antibody test in the field

Abstract

The seroprevalence of COVID-19 infection among graduates, professors and staffs attending the royal graduation ceremony determined from this study helps to establish COVID-19 screening recommendation for mass gatherings using rapid antibody tests. Department of Disease Control together with Sakon Nakhon Provincial Health Office performed COVID-19 serosurvey for the graduation ceremony attendees. Out of 15,684 attendees who were tested by rapid COVID-19 antibody test, 299 were tested positive (1.91%). 31.8% of 107 positive attendees who answered the questionnaires had either COVID-19 infection risks or symptoms since January 2020. Most of them had a history of returning from an area with outbreak within Thailand (13.1%). 202 rapid test-positive attendees were tested further by chemiluminescence immunoassay (CLIA) and microneutralization assay (MNA). Only one person was reactive to SARS-CoV-2 antibodies by CLIA and no antibodies was detected by microneutralization assay (MNA).

Field interpretation of rapid antibody test should be done with caution, especially in population with low COVID-19 prevalence. COVID-19 rapid antibody test has a low positive predictive value when comparing to CLIA and MNA, causing people without significant risk of COVID-19 being unnecessarily tested by RT-PCR. Antibody testing cannot substitute the gold standard RT-PCR method in diagnosing COVID-19 infection. Screening for COVID-19 exposure risks before the graduation ceremony should be done. If risk is present, RT-PCR testing should be performed regardless of the rapid test results.