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Cepheid Xpert Ebola assay accurately detects Ebola virus in semen
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The Cepheid Xpert Ebola assay test accurately and precisely detected Ebola virus in semen, according to a study recently published in the Journal of Infectious Diseases.
“Reports of Ebola viral RNA detected in semen in Ebola Virus Disease (EVD) survivors and at least one case of documented sexual transmission of the virus has led to interest in detecting [Ebola virus (EBOV)] in other body fluids, particularly genital secretions,” Amy James Loftis, of the division of infectious diseases at University of North Carolina, Chapel Hill, and colleagues wrote, noting that WHO recommended men refrain from sex for a year after recovery from Ebola or until their semen tested EBOV-free. “However, despite this recommendation and the need for accurate testing for EBOV in this and other body fluids, no fully validated assay for EBOV detection in fluids other than blood is available.”
The researchers collected 175 samples of blood and semen from uninfected men at Phebe Hospital PCR Laboratory in Bong County, Liberia, spiking 150 samples with EBOV. Because the Cepheid GeneXpert PCR assay had already been validated for blood testing, they verified the test’s sensitivity and repeatability using 20 negative donor samples and 40 spiked samples.
The limit of detection was 275 copies/mL in blood and 1,000 copies/mL in semen samples, the researchers reported, with detection limits increasing alongside the intervals between collection and testing. They also reported that at least one target gene included in the assay could still be detected three days after collection, meaning acceptable results were obtained as much as 72 hours after sample collection. The un-spiked samples were all undetected.
Loftis and colleagues noted, however, that an undetectable test result did not necessarily mean the disease was absent because there is no minimum threshold established to determine the viral load necessary to transmit EBOV through semen. The researchers recommended that “counseling and clinical decision-making should incorporate messaging regarding the limitations of the assay when it is used.
“These results support the expanded use of this assay to detect Ebola in the semen and blood to guide individual and public health responses during and following an outbreak of this virus,” Loftis and colleagues wrote. - by Andy Polhamus
Disclosure: The researchers report no relevant financial disclosures.
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