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.

Evaluation of a rapid and sensitive RT-qPCR assay for the detection of Ebola Virus.

BACKGROUND: The 2013-2016 Ebola virus disease (EVD) outbreak showed a lack of diagnostic point-of-care methods. Currently, EBOV diagnosis relies on quantitative reverse-transcription-PCR (RT- qPCR), highly specific and sensitive, but requiring skilled personnel and well-equipped laboratories. In field settings, these factors and others, such as samples' time of collection and transportation, determine a prolonged turnaround-time to final results. In outbreak scenarios, a rapid and transportable method could eliminate issues of cohorting suspected and actual EVD patients for lack of diagnostic certainty. The aim of this study was the field evaluation of the new fast, easy-to-use and reliable RT-qPCR assay and platform for EBOV detection, developed in the framework of the EbolaMoDRAD project by CLONIT S.r.l. and STMicroelectronics S.r.l. STUDY DESIGN: We evaluated its performance during the outbreak and in further studies in the EVD laboratory at the Princess Christian Maternity Hospital (PCMH) in Freetown (Sierra Leone) run by Emergency NGO and the Italian National Institute for Infectious Diseases (INMI). The assay was tested on residual aliquots of clinical specimens from EBOV-positive or -negative patients (n=116, EVD prevalence 37%). RESULTS AND CONCLUSION: Overall, the test was very easy-to-use and the instrument was robust and reliable in field-settings. The sensitivity of the assay was 100% and the specificity was 98.63% (95%CI: 96.34-100.92%). The positive and negative predictive values were 97.73 (95%CI:94.77-100.68%) and 100%, respectively. The high sensitivity and specificity of this new assay indicate that it is promising for laboratory diagnosis, especially in resource-limited settings.