A new fingerprick test given at the patient’s bedside predicts Ebola infection within minutes, representing a significant improvement in diagnosing the disease which has killed thousands in West Africa.
Research published today in The Lancet presents a rapid diagnostic test (RDT) - developed by medical diagnostic giant Corgenix - that gives an almost immediate answer to a patient’s status of Ebola virus disease and replaces the current costly, time-consuming laboratory method.
To diagnose Ebola in West Africa at present, health workers intravenously collect a vial of the patient’s blood, then test it in a laboratory using a method called a reverse transcription polymerase chain reaction (RT-PCR).
The molecular technique detects the virus' genetic code and is also used to diagnose other infectious diseases such as HIV.
But molecular testing requires a large, well-resourced laboratory and in a setting such as Sierra Leone where the research was conducted, result turnaround times can take several days. Transportation and testing also puts health-care workers and laboratory technicians at serious risk.
Researchers say the new ReEBOV Antigen Rapid Diagnostic Test is capable of detecting the virus using just a small drop of blood at the patient’s bedside.
Director of the Doherty Institute for Infection and Immunity at the University of Melbourne, Sharon Lewin, said point-of-care tests such as the RDT were “hugely important” for controlling diseases such as Ebola.
“Even though the current Ebola crisis is over, Ebola has been around since the 1970s and it will come around again. These sort of tests can make an enormous difference and prevent us seeing an epidemic of this scale again,” said Dr Lewin, who was not involved in the study.
“I would put the discovery of the bedside test almost up there with effective treatments,” she added.
Researchers tested 106 suspected Ebola patients admitted to two treatment centres in Sierra Leone during February 2015. They analysed a fingerstick blood sample taken at the bedside with the new test as well as a full blood sample, taken intravenously, with standard RT-PCR. They then compared the two results.
Further, they performed the new test in a laboratory using whole blood samples collected intravenously from 284 patients. Again, they compared these results with their molecular testing results.
The 25 patients who tested positive for Ebola at the bedside also showed a positive result when their blood sample was analysed through the molecular method. The 45 patients who were confirmed to have Ebola at the laboratory with the old test also showed a positive result when researchers analysed their whole blood sample at the laboratory.
Article co-author Dr Nira Pollock, Assistant Professor at Harvard Medical School, said the findings were better than expected.
“We show that the test performed very well with 100% sensitivity in our population of people who were symptomatic and who had had symptoms for about three days.”
But she said it was important to understand this test, like any diagnostic test, wasn’t perfect.
“One of the particular problems they had is that it’s not really clear the test that they’re comparing with is actually a gold standard, so when there’s a discordance with the tests, you can’t tell which one is actually right,” said Professor in Infectious Diseases Epidemiology at Monash University, Dr Allen Cheng.
Dr Cheng, who was not involved in the study, said that the test would likely be used as a provisional positive and further testing, using the original molecular method would be required to validate the results.
“It had a 100% success rate in picking up people who did have Ebola, so all the people who did have Ebola had a positive test, but not all the people who tested positive had Ebola.”
Dr Pollock said that the new test would prove very effective as aid organisations started pulling out of West Africa.
“The availability of molecular testing right now is quite good because all the international labs are there, but over time nobody thinks all those labs are going to stay and the place is going to want to catch new cases in peripheral areas.”
Although West African countries have left the worst of the recent outbreak behind them, Sierra Leone and Guinea are still seeing some infection, with around 20 to 27 fresh Ebola cases being confirmed weekly.
Authors: The Conversation