EBOLA Ag K-SeT rapid test: field evaluation in Sierra Leone

Objectives Efficient interruption of Ebola virus disease (EVD) transmission chains critically depends on reliable and fast laboratory diagnosis. We evaluated the performance of the EBOLA Virus Antigen Detection K-SeT (EBOLA Ag K-SeT), a new rapid diagnostic antigen test in field settings. Methods The study was conducted in a field laboratory located in Freetown (Sierra Leone) by the Italian National Institute for Infectious Diseases ‘L. Spallanzani’ and the EMERGENCY Onlus NGO. The EBOLA Ag K-SeT was tested on 210 residual plasma samples (EVD prevalence 50%) from patients hospitalized at the EMERGENCY Ebola treatment center in Goderich (Freetown), comparing the results with quantitative real-time PCR. Results Overall, the sensitivity of EBOLA Ag K-SeT was 88.6% (95% confidence interval (CI), 82.5–94.7), and the corresponding specificity was 98.1% (95% CI, 95.5–100.7). The positive and negative predictive values were 97.9% (95% CI, 95.0–100.8) and 89.6% (95% CI, 84–95.2), respectively. The sensitivity strongly increased up to 98.7% (95% CI, 96.1–101.2) for those samples with high virus load (≥6.2 log RNA copies/mL). Conclusions Our results suggest that EBOLA Ag K-SeT could represent a new effective diagnostic tool for EVD, meeting a need for resource-poor settings and rapid diagnosis for individuals with suspected EVD.