Variation across population subgroups of COVID-19 antibody testing performance

Understanding variations in the performance of serological tests for SARS-CoV-2 across varying demographics is relevant to clinical interpretations and public policy derived from their results. Appropriate use of serological assays to detect anti-SARS-CoV-2 antibodies requires estimation of their accuracy over large populations and an understanding of the variance in performance over time and across demographic groups. In this manuscript we focus on anti-SARS-CoV-2 IgG, IgA, and IgM antibody tests approved under emergency use authorizations and determine the recall of the serological tests compared to RT-PCR tests by Logical Observation Identifiers Names and Codes (LOINCs). Variability in test performance was further examined over time and by demographics. The recall of the most common IgG assay (LOINC 94563-4) was 91.2% (95% CI: 90.5%, 91.9%). IgA (LOINC 94562-6) and IgM (94564-2) assays performed significantly worse than IgG assays with estimated recall rates of 20.6% and 27.3%, respectively. A statistically significant difference in recall (p = 0.019) was observed across sex with a higher recall in males than females, 92.1% and 90.4%, respectively. Recall also differed significantly by age group, with higher recall in those over 45 compared to those under 45, 92.9% and 88.0%, respectively (p< 0.001). While race was unavailable for the majority of the individuals, a significant difference was observed between recall in White individuals and Black individuals (p = 0.007) and White individuals and Hispanic individuals (p = 0.001). The estimates of recall were 89.3%, 95.9%, and 94.2% for White, Black, and Hispanic individuals respectively.