Objectives: To avoid the significant risks posed by the use of COVID-19 serology tests with supply chain constraints or poor performance characteristics, we developed an in-house SARS-CoV-2 total antibody test. Our test was compared with three commercial methods, and was used to determine COVID-19 seroprevalence among healthcare workers and outpatients in Minnesota. Methods: Seventy-nine plasma and serum samples from 50 patients 4–69 days after symptom onset who tested positive by a SARS-CoV-2 PCR method using a nasopharyngeal (NP) swab were used to evaluate our test's clinical performance. Seropositive samples were analyzed for IgG titers in a follow-up assay. Thirty plasma and serum from 12 patients who tested negative by a SARS-CoV-2 PCR method using a nasopharyngeal (NP) swab and 210 negative pre-pandemic serum samples were also analyzed. Among samples from patients > 14 days after symptom onset, the assay had 100% clinical sensitivity and 100% clinical specificity, 100% positive predictive value and 100% negative predictive value. Analytical specificity was 99.8%, indicating minimal cross-reactivity. A screening study was conducted to ascertain COVID-19 seroprevalence among healthcare workers and outpatients in Minnesota. Results: Analysis of serum collected between April 13 and May 21, 2020 indicated a COVID-19 seroprevalence of 2.96% among 1,282 healthcare workers and 4.46% among 2,379 outpatients. Conclusions: Our in-house SARS-CoV-2 total antibody test can be used to conduct reliable epidemiological studies to inform public health decisions during the COVID-19 pandemic.
Bibliographical noteFunding Information:
The authors gratefully acknowledge the following individuals for their contributions to this study: Dr. Fang Li (Professor, Department of Veterinary and Biomedical Sciences, University of Minnesota) for donating the RBD antigen used for the ELISA method; members of the labs of Drs. Marc Jenkins, Tyler Bold, Fang Li, and Bharat Thyagarajan; Steve J. Story (Technical Specialist, M Health Fairview Special Chemistry Laboratory), Christine K. Senn (Laboratory Manager, M Health Fairview University of Minnesota Medical Center West Bank Laboratory), Robert Janicek (Business Manager, University of Minnesota Advanced Research and Diagnostic Laboratory), Emily Kokaisel (Chemistry Technical Specialist, M Health Fairview University of Minnesota Medical Center East Bank Laboratory), Stephanie McGlone (Manager of Laboratory Services, M Health Fairview Bethesda and St. Joseph's Hospital), and the M Health Fairview COVID-19 System Command Center.
© 2021 The Canadian Society of Clinical Chemists
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