Author Interviews, Ebola, Lancet / 02.07.2015
New Rapid Test For Ebola May Be Useful In High-Risk Populations
MedicalResearch.com Interview with:
Jana Broadhurst, MD, PhD
Stanford University
Nira R Pollock MD PhD
Boston Children's Hospital, Boston, MA
Medical Research: What is the background for this study? What are the main findings?
Response: At present, diagnosis of Ebola virus disease (EVD) in west Africa requires transport of venipuncture blood to field laboratories for testing by real-time RT-PCR, resulting in delays that complicate patient care and infection control efforts. Therefore, an urgent need exists for a point-of-care rapid diagnostic test (RDT) for this disease. In this study, we performed a field validation of the Corgenix ReEBOV Antigen Rapid Test kit, the only Ebola RDT authorized for emergency use by the WHO and FDA. This test is a dipstick lateral flow immunoassay designed to detect the Ebola virus VP40 protein in whole blood (collected by either fingerstick or whole blood) or plasma.
We performed the rapid diagnostic test at the point-of-care on fingerstick blood samples from 106 individuals with suspected EVD presenting at two Ebola clinical centers in Sierra Leone. Separately, we performed the RDT on 284 venous whole blood samples submitted to the Public Health England field reference laboratory for clinical testing. Two readers independently scored each RDT as positive, negative, or invalid, with any disagreements resolved by a third. RDT results were compared with clinical real-time RT-PCR results obtained with the RealStar Filovirus RT-PCR kit 1.0 (altona Diagnostics GmBH).
In point-of-care testing of fingerstick blood, the RDT had 100% sensitivity (95% CI 87.7-100) and 92% specificity (95% CI 83.8-97.1). Similarly, in venipuncture blood tested in the reference laboratory the rapid diagnostic test had 100% sensitivity (95% CI 92.1-100) and 92% specificity (95% CI 88.0-95.3). The two independent readers agreed for 95.2% of point-of-care and 98.6% of reference laboratory RDT results. The maximum cycle threshold (Ct) value was 26.3 in PCR-positive samples tested from both point-of-care (mean Ct 22.6) and reference laboratory (mean Ct 21.5) cohorts. Six of 16 banked plasma samples from RDT-positive and altona-negative patients were positive by an alternative real-time RT-PCR assay (the Trombley assay); 3 of 18 samples from individuals who were negative by both the RDT and altona test were also positive by Trombley.
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