{"doi":"10.1101/2021.03.08.21252784","title":"SARS-CoV-2 seroassay optimization and performance in a population with high background reactivity in Mali","abstract":"Serological tests are an indispensable tool to understand the epidemiology of the SARS-CoV-2 pandemic, particularly in areas where molecular diagnostics are limited. Poor assay performance may hinder the utility of these tests, including high rates of false-positivity previously reported in sub-Saharan Africa. From 312 Malian samples collected prior to 2020, we measured antibodies to the commonly tested SARS-CoV-2 antigens and four other betacoronaviruses by ELISA, and assessed functional cross-reactivity in a subset by SARS-CoV-2 pseudovirus neutralization assay. We then evaluated the performance of an ELISA developed in the US, using two-antigen SARS-CoV-2 spike protein and receptor-binding domain. To optimize test performance, we compared single and two-antigen approaches using existing assay cutoffs and population-specific cutoffs for Malian control samples (positive and negative). Background reactivity to SARS-CoV-2 antigens was common in pre-pandemic samples compared to US controls (43.4% (135/311) for spike protein, 22.8% (71/312) for RBD, and 33.9% (79/233) for nucleocapsid protein). SARS-CoV-2 reactivity correlated weakly with other betacoronavirus reactivity, varied between Malian communities, and increased with age. No pre-pandemic samples demonstrated functional activity. Regardless of the cutoffs applied, specificity improved using a two-antigen approach. Test performance was optimal using a two-antigen assay with population-specific cutoffs derived from ROC curve analysis [Sensitivity: 73.9% (51.6-89.8), Specificity: 99.4% (97.7-99.9)]. In the setting of high background reactivity, such as sub-Saharan Africa, SARS-CoV-2 serological assays need careful qualification is to characterize the epidemiology of disease, prevent unnecessary harm, and allocate resources for targeted control measures.","journal":"medRxiv","year":2021,"id":213836,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":14,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.962,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2021-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":339093,"name":"John Woodford","orcid":"0000-0002-8363-5495","position":1,"is_corresponding":false},{"id":334203,"name":"Alassane Dicko","orcid":"0000-0003-2153-8427","position":2,"is_corresponding":false},{"id":645894,"name":"Amatigué Zéguimé","orcid":"0000-0002-3158-1907","position":3,"is_corresponding":false},{"id":671317,"name":"M’Bouye Doucoure","orcid":"0000-0003-1161-0915","position":4,"is_corresponding":false},{"id":564284,"name":"Jennifer Kwan","orcid":"0000-0002-7176-6340","position":5,"is_corresponding":false},{"id":395417,"name":"Irfan Zaidi","orcid":"0000-0001-9161-2050","position":6,"is_corresponding":false},{"id":414017,"name":"Justin Doritchamou","orcid":"0000-0002-4589-7216","position":7,"is_corresponding":false},{"id":415002,"name":"Maryonne Snow-Smith","orcid":null,"position":8,"is_corresponding":false},{"id":396435,"name":"Nada Alani","orcid":null,"position":9,"is_corresponding":false},{"id":569231,"name":"Jonathan P. Renn","orcid":null,"position":10,"is_corresponding":false},{"id":689133,"name":"Ivan Košík","orcid":"0000-0001-5756-5182","position":11,"is_corresponding":false},{"id":261944,"name":"Jaroslav Hollý","orcid":"0000-0002-0589-9655","position":12,"is_corresponding":false},{"id":17894,"name":"Jonathan W. Yewdell","orcid":"0000-0002-3826-1906","position":13,"is_corresponding":false},{"id":267809,"name":"Dominic Esposito","orcid":"0000-0002-9987-1687","position":14,"is_corresponding":false},{"id":238245,"name":"Kaitlyn Sadtler","orcid":"0000-0003-2587-8330","position":15,"is_corresponding":false},{"id":236042,"name":"Patrick E. Duffy","orcid":"0000-0002-4483-5005","position":16,"is_corresponding":false},{"id":334202,"name":"Issaka Sagara","orcid":"0000-0002-8555-9983","position":0,"is_corresponding":true}],"reference_count":29,"raw_metadata":null,"created_at":"2026-07-18T23:52:41.672172Z","pmid":"33758883","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}