Cross-Reactivity of Two SARS-CoV-2 Serological Assays in a Setting Where Malaria Is Endemic
Laura C. Steinhardt, Fehintola Ige, Nnaemeka C. Iriemenam, Stacie M. Greby, Yohhei Hamada, Mabel Uwandu, Maureen Aniedobe, Kristen A. Stafford, Alash’le Abimiku, Nwando Mba, Ndidi Agala, Olumide Okunoye, Augustine O. Mpamugo, Mahesh Swaminathan, Edewede Onokevbagbe, Temitope Olaleye, Ifeanyichukwu Odoh, Barbara J. Marston, McPaul Okoye, Ibrahim Abubakar, Molebogeng X. Rangaka, Eric Rogier, Rosemary Audu
Abstract
IgG levels were significantly higher among false positives for both Abbott and Euroimmun; no association was found with active Plasmodium falciparum infection. An avidity assay using various concentrations of urea wash in the Euroimmun assay reduced loosely bound IgG: of 37 positive/borderline prepandemic samples, 46%, 86%, 89%, and 97% became negative using 2 M, 4 M, 5 M, and 8 M urea washes, respectively. The wash slightly reduced avidity of antibodies from SARS-CoV-2 patients within 28 days of PCR confirmation; thereafter, avidity increased for all urea concentrations except 8 M. This validation found moderate to substantial cross-reactivity on two SARS-CoV-2 serological assays using samples from a setting where malaria is endemic. A simple urea wash appeared to alleviate issues of cross-reactivity.