FROM THE LANCET
The new ReEBOV Antigen Rapid Test kit for Ebola virus may be better at catching cases than the current method used for diagnosis, according to a study of people living in Sierra Leone with Ebola symptoms.
The study was the first point-of-care assessment of the ReEBOV test kit, which is the only rapid diagnostic test for Ebola virus to obtain emergency use authorization from the World Health Organization and the U.S. Food and Drug Administration. The cases of Ebola found using the new test were compared with results of the real-time RT-PCR test, the standard method for diagnosing Ebola. While the ReEBOV test can provide results within minutes, obtaining a diagnosis with the RT-PCR requires transport of venipuncture blood to field biocontainment laboratories.
Point-of-care testing of fingerstick blood samples from 106 individuals were performed using the new rapid diagnostic test. (Two independent readers scored each rapid diagnostic test, with any disagreements resolved by a third reader.) The results were then compared with testing of venipuncture plasma in a reference laboratory by altona Diagnostics’ real-time RT-PCR. Separately, the rapid diagnostic test was performed on whole blood and the RT-PCR was performed on plasma from 284 patients that were sent to the laboratory from various clinical sites.
Comparing the results of the rapid diagnostic test to those of the RT-PCR indicated that the new test was 100% sensitive and 92% specific. In point-of-care testing, all 28 patients who tested positive for Ebola virus by RT-PCR were also positive by fingerstick rapid diagnostic test. These results also showed that 71 of 77 patients who tested negative by RT-PCR were also negative by the rapid diagnostic test. In laboratory testing, all 45 specimens that tested positive by RT-PCR were also positive by the rapid diagnostic test, and 214 of 232 specimens that tested negative by RT-PCR were also negative by the rapid diagnostic test.
While the rapid diagnostic test detected all patients who were positive for Ebola by the standard test, the RT-PCR “had imperfect sensitivity,” which “probably caused us to overestimate the true sensitivity of the rapid diagnostic test,” noted Dr. Mara Jana Broadhurst and her colleagues.
The altona RT-PRC failed to detect a small number of Ebola cases that tested positive both by the rapid diagnostic test and an alternative RT-PCR test (Trombley).
“Given the limitations of the performance of the altona RT-PCR reference test in patients with low levels of the virus in their blood, more research is needed to assess how the new [rapid diagnostic test] will perform in patients very early in the course of [the Ebola virus disease],” the researchers said in a written statement.
Read the full study and commentary in The Lancet .
klennon@frontlinemedcom.com
