Clinical evaluation of commercial SARS-CoV-2 serological assays in a malaria endemic setting

The levels of immune response to SARS-CoV-2 infection or vaccination are poorly understood in African populations and is complicated by cross-reactivity to endemic pathogens as well as differences in host responsiveness. To begin to determine the best approach to minimize false positive antibody levels to SARS-CoV-2 in an African population, we evaluated three commercial assays, namely Bio-Rad Platelia SARS-CoV-2 Total Antibody (Platelia), Quanterix Simoa Semi-Quantitative SARS-CoV-2 IgG Antibody Test (anti-Spike), and the GenScript cPass™ SARS-CoV-2 Neutralization Antibody Detection Kit (cPass) using samples collected in Mali in West Africa prior to the emergence of SARS-CoV-2. A total of one hundred samples were assayed. The samples were categorized in two groups based on the presence or absence of clinical malaria. Overall, thirteen out of one hundred (13/100) samples were false positives with the Bio-Rad Platelia assay and one of the same one hundred (1/100) was a false positive with the anti-Spike IgG Quanterix assay. None of the samples tested with the GenScript cPass assay were positive. False positives were more common in the clinical malaria group, 10/50 (20%) vs. the non-malaria group 3/50 (6%); p = 0.0374 using the Bio-Rad Platelia assay. Association between false positive results and parasitemia by Bio-Rad remained evident, after adjusting for age and sex in multivariate analyses. In summary, the impact of clinical malaria on assay performance appears to depend on the assay and/or antigen being used. A careful evaluation of any given assay in the local context is a prerequisite for reliable serological assessment of anti-SARS-CoV-2 humoral immunity.