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, that were 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 done 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 lack of algorithms. 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.