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Point-of-Care Ebola Test Found Accurate in Field Test

Ebola clinic

Woman being evaluated at an Ebola clinic in Sierra Leone (Rebecca Rollins, Partners In Health)

26 June 2015. A commercial point-of-care test detecting Ebola virus in the blood of a patient was shown in a field test in Sierra Leone to be as accurate as tests sent to remote labs for analysis. Results of the study led by Nira Pollock of Harvard Medical School and Boston Children’s Hospital were published yesterday in the journal The Lancet (registration required).

While the number of Ebola cases in the West African countries of Guinea, Liberia, and Sierra Leone are considerably fewer than the height of the current outbreak in Fall 2014, World Health Organization says that 20 to 27 new cases are reported each week since the end of May 2015. Clinicians diagnosing people for Ebola, however, are still hampered by the amount time needed to confirm an individual has the virus.

Current test procedures require taking a vial of blood from the individual and sending it, under strict protective procedures, to a lab for analysis. The analysis looks for RNA in the sample with a genetic technique known as reverse transcription-polymerase chain reaction, or RT-PCR, and in many cases requires days to return results before patients can receive care and possibly infecting others.

Pollock and colleagues — from Harvard, Boston Children’s Hospital, and the advocacy group Partners in Health — tested an alternative method made by diagnostics company Corgenix Inc. in Broomfield, Colorado. The Corgenix test uses a self-contained device similar to a home-pregnancy test, and takes a smaller sample of blood from a fingerstick. The device tests the blood sample for a specific antigen protein, VP40, encoded by Ebola viruses, which indicates the presence of Ebola in the patient’s blood, typically in 15 to 25 minutes. Corgenix provided test kits, but were otherwise not involved in the study.

The researchers evaluated the device in February 2015 at two Partners in Health clinics in Sierra Leone, where samples from 106 individuals suspected of having the Ebola virus were analyzed by both the Corgenix point-of-care technique and conventional methods at a Sierra Leone lab. The researchers devised a process for two clinicians to verify the point-of-care readings — made more difficult in some cases by the protective gear — with a third colleague called in if the first two clinicians disagreed.

The findings show all 28 people testing positive for Ebola by the point-of-care technique also returned positive results from the lab analysis. Of the 77 individuals testing negative for Ebola in the lab analysis, 71 or 92 percent also tested negative with the point-of-care technique.

The researchers as well evaluated the Corgenix technique with blood samples collected and analyzed by conventional lab techniques from 284 separate cases throughout Sierra Leone at that time. The separate review returned identical results, where all of the cases testing positive with the point-of-care technique also tested positive using conventional lab methods. Likewise, 92 percent of the samples testing negative through lab methods also tested negative with point-of-care techniques.

The study did point out, however, some limitations in both methods. An analysis using alternative lab methods not available for wide usage found a small number of cases where low levels of Ebola virus went undetected by both the point-of-care and conventional lab tests. Thus, say the researchers, more evaluations of these techniques may be needed to detect Ebola in its earliest stages, particularly in challenging environments.

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