Field Evaluation of the Performance of a SARS-CoV-2 Antigen Rapid Diagnostic Test in Uganda using Nasopharyngeal Samples

Nalumansi, Aminah; Lutalo, Tom; Kayiwa, John; Watera, Christine; Balinandi, Stephen; Kiconco, Jocelyn; Nakaseegu, Joweria; Olara, Denis; Odwilo, Emmanuel; Serwanga, Jennifer; Kikaire, Bernard; Ssemwanga, Deogratius; Nabadda, Susan; Ssewanyana, Isaac; Atwine, Diane; Mwebesa, Henry; Bosa, Henry Kyobe; Nsereko, Christopher; Cotten, Matthew; Downing, Robert; Lutwama, Julius; Kaleebu, Pontiano

OBJECTIVES: There is a high demand for SARS-CoV-2 testing to identify COVID-19 cases. Real-time, quantitative PCR (qRT-PCR) is the recommended diagnostic test but a number of constraints, including cost prevent its widespread implementation. The aim of this study was to evaluate a low cost, easy-to-use rapid antigen test for diagnosing COVID-19 at the point-of-care. METHODS: Nasopharyngeal swabs from suspect COVID-19 cases and from low-risk volunteers were tested on the STANDARD Q COVID-19 Ag Test and results compared with the qRT-PCR results. RESULTS: 262 samples were collected including 90 qRT-PCR positives. The majority were from males (89%) with a mean age of 34 years and only 13 (14%) of the positives were mildly symptomatic. Sensitivity and specificity of the antigen test were 70.0% (95% CI: 60 - 79) and 92% (95% CI: 87 - 96) respectively; diagnostic accuracy was 84% (95% CI: 79 - 88). The antigen test was more likely to be positive in samples with qRT-PCR Ct values ≤29 reaching a sensitivity of 92%. CONCLUSIONS: The STANDARD Q COVID-19 Ag Test performed less than optimally in this evaluation. However, the test may still have an important role to play early in infection when timely access to molecular testing is not available but results should be confirmed by qRT-PCR.