Development and comparative evaluation of SARS-CoV-2 S-RBD and N based ELISA tests in various African endemic settings

Management of the COVID-19 pandemic relies on molecular diagnostic methods supported by serological tools. Herein, we developed S-RBD-and N-based ELISA assays useful for infection rate surveillance as well as the follow-up of acquired protective immunity against SARS-CoV-2. ELISA assays were optimized using COVID-19 Tunisian patients' sera and prepandemic controls. Assays were further validated in 3 African coun-tries with variable endemic settings. The receiver operating curve was used to evaluate the assay performances. The N-and S-RBD-based ELISA assays performances, in Tunisia, were very high (AUC: 0.966 and 0.98, respectively, p < 0.0001). Cross-validation analysis showed similar performances in different settings. Cross-reactivity, with malaria infection, against viral antigens, was noticed. In head-to-head comparisons with dif-ferent commercial assays, the developed assays showed high agreement. This study demonstrates, the added value of the developed serological assays in low-income countries, particularly in ethnically diverse popula-tions with variable exposure to local endemic infectious diseases.(c) 2023 Elsevier Inc. All rights reserved.