Investigation of COVID-19 Serology in a Tertiary Care Center

Abstract

Purpose: This study aimed to screen the patients admitted to our hospital for SARS-CoV-2 specific antibodies after a PCR test and understand the local serological profile. Materials and Methods: The patients tested for anti-SARS-CoV-2 IgG and/or IgM between January-June 2021 were included in the study. SARS-CoV-2 PCR test was performed simultaneously. Results: Either IgM or IgG alone was requested in 123 of 725 patients, and IgM and IgG together in 602. The PCR test was positive in 40 (13%) of 304 (42%) patients who had a PCR test after 30 days of the serology request. Of these PCR-positive patients, 60% had IgM and IgG antibodies together, whereas among 204 PCR-negative patients, 64% tested negative for IgM and IgG. 58% of the tests were ordered without a PCR request. The period between PCR and serology testing was as follows: 233 (76.6%) in 7 days, 27 (8.8%) in 8-14 days, 7 (2.3%) in 15-21 days, and 37 (12.3%) in 22-30 days. 117 (38.5%) of the requests were made simultaneously. Conclusion: WHO recommends that serology testing should be performed after the 1st and 3-4th week of the initial PCR test. The high rate of inappropriate testing demonstrates a lack of algorithms. The use of serological tests is recommended in conjunction with nucleic acid tests but not to be used alone in the diagnosis of COVID-19. Our results demonstrated the high rate of unnecessary requests for serology testing to determine the antibody response against SARS-CoV-2 vaccines.