Performance of a rapid antigen test for SARS-CoV-2 in Kenya
Simon Onsongo, Kephas Otieno, Shannen van Duijn, Emily R. Adams, Mervis Omollo, Isdora A. Odero, Alloys K’Oloo, Nathalie Houben, Emmanuel Milimo, Robert Aroka, Hellen C. Barsosio, Fredrick Oluoch, Albert Odhiambo, Simon Kariuki, Tobias F. Rinke de Wit
Abstract
Testing for SARS-CoV-2 in resource-poor settings remains a considerable challenge. Gold standard nucleic acid tests are expensive and depend on availability of expensive equipment and highly trained laboratory staff. More affordable and easier rapid antigen tests are an attractive alternative. This study assessed field performance of such a test in western Kenya. We conducted a prospective multi-facility field evaluation study of NowCheck COVID-19 Ag-RDT compared to gold standard PCR. Two pairs of oropharyngeal and nasopharyngeal swabs were collected for comparative analysis. With 997 enrolled participants the Ag-RDT had a sensitivity 71.5% (63.2-78.6) and specificity of 97.5% (96.2-98.5) at cycle threshold value <40. Highest sensitivity of 87.7% (77.2-94.5) was observed in samples with cycle threshold values ≤30. NowCheck COVID-19 Ag-RDT performed well at multiple healthcare facilities in an African field setting. Operational specificity and sensitivity were close to WHO-recommended thresholds.