The Lancet has published details of a new point-of-care test for Ebola virus that is as sensitive as the conventional laboratory test, but provides results within minutes.
In order to confirm Ebola virus infection, a blood sample currently has to be sent to a laboratory with a high level of biosafety and staff expertise. The sample is then tested for the presence of Ebola virus using a complex and time-consuming technique - reverse transcription polymerase chain reaction (RT-PCR) - that exposes healthcare workers to the potential risk of contracting Ebola virus from the samples being tested. Furthermore, the delay in obtaining confirmation of Ebola infection hindered efforts to prevent the spread of the Ebola epidemic in west Africa.
Microscopic view of Ebola Virus, Copyright: Nixx Photography, Image ID: 210066871 via Shutterstock.com
The newly developed rapid diagnostic test for Ebola virus (ReEBOV Antigen Rapid Test; Corgenix), which can be performed on the spot (using a fingerstick blood sample) will allow individuals who have contracted Ebola to be identified quickly. This in turn allows earlier identification and testing of people who have been in recent contact with the Ebola patient, whereby helping contain the spread of Ebola.
Dr Nira Pollock, senior author and Associate Medical Director of the Infectious Diseases Diagnostic Laboratory at the Boston Children’s Hospital, USA explained “Laboratory results can sometimes take days to return. Delays like this result not only in the failure to diagnose and treat Ebola-infected patients, but also in individuals without Ebola being admitted to holding units where they may be subsequently infected with the virus…This new test, on the other hand, is capable of detecting the Ebola virus in just a small drop of blood tested at the bedside, and could help us in the fight against Ebola.”
The diagnostic accuracy of the new test was compared with the conventional RT-PCR test in a clinical study conducted in the field reference laboratory run by Public Health England at Port Loko in Sierra Leone earlier this year. Over a hundred individuals with suspected Ebola infection were tested using both the conventional laboratory test and the new point-of-care test. In addition, 284 samples were tested using both tests in the laboratory.
The new test was shown to have 100% sensitivity, identifying all the Ebola infections detected by conventional testing. It also had 92% specificity in identifying patients who were not infected with Ebola virus.
Co-author Dr Jana Broadhurst from Partners In Health, Boston, USA commented “This test could have an immediate impact on patient care and infection control by reliably detecting patients well into their illness who are likely to be highly infectious. Earlier test results would improve triage of patients, enabling staff to focus on those most likely to have Ebola, and reducing the opportunity for infection of non-Ebola ‘suspects’”.
However, the study also revealed that there were discrepancies between different RT-PCR tests when there are very low levels of Ebola virus in a sample. Further research is thus needed to assess how the new diagnostic test will perform in patients very recently infected with Ebola virus.