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HCV finger-stick test accurate, gives results in 1 hour

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March 14, 2018

A new hepatitis C virus finger-stick test can be used to diagnose infection in a single clinical visit, delivering results in 1 hour, according to researchers.

The Xpert HCV Viral Load Finger Stick (Xpert VL FS, Cepheid) assay accurately detected active infection with HCV in point-of-care blood samples, they wrote in The Journal of Infectious Diseases. The results provide a way for clinicians to reduce the number of visits needed to diagnose HCV, they added.

“This provides a major advance over antibody-based point-of-care tests, which only indicate HCV exposure,” researcher François M. J. Lamoury, senior research officer at the University of New South Wales Kirby Institute in Sydney, Australia, and colleagues wrote. “Further, the novel Xpert VL FS assay provides a substantial advance over the [current] Xpert HCV Viral Load assay, avoiding the need for plasma separation and enabling testing and diagnosis in 1 hour as compared to 2 hours, increasing the potential to move toward a single-visit diagnosis.”

Current HCV testing includes two clinical visits, the researchers noted. In the first visit, clinicians test for HCV antibodies, which would confirm only that the patient has been exposed to the virus. A second visit includes testing for HCV RNA to determine the presence of active infection. Lamoury and colleagues cited previous studies showing that patients are lost to follow up because they do not return for subsequent visits, and that the process can be difficult without a phlebotomist and for people who inject drugs (PWID), whose veins can be difficult to access.

The new Xpert HCV VL FS assay is a redesigned version of the Xpert HCV Viral Load assay that is capable of testing a 100 µL sample of capillary blood.

To test the newer assay’s potential to make diagnosis more convenient, the researchers enrolled participants between Aug. 3, 2016, and Dec. 13, 2016, at three drug treatment clinics and a service for homeless people in Australia. Each participant received a voucher worth 20 Australian dollars.

The participants gave finger-stick capillary blood samples to be tested by Xpert HCV VL FS. They also gave venipuncture samples — the standard of care for HCV RNA testing —  to be tested with the old Xpert assay. Participants also provided information about drug use and their knowledge of liver disease and HCV in a self-administered survey.

A total of 223 participants enrolled, 72% of whom had a history of injection drug use, and 46% of whom had injected within the previous month of enrollment. Of the 210 participants with available Xpert HCV Viral Load test results, 40% had detectable HCV RNA.

The older assay’s sensitivity and specificity for HCV RNA quantification were both 100% (95% CI, 96.9-100 and 95% CI, 94.4-100, respectively). The Xpert HCV VL FS assay also had 100% sensitivity and specificity for HCV RNA quantification (95% CI, 93.9-100 and 95% CI, 96.6-100, respectively).

“The finger-stick Xpert HCV VL FS test should be further evaluated as a screening tool for HCV RNA detection in high-prevalence settings, particularly in services for PWID,” they wrote. “In addition to broad direct-acting antiviral uptake, efforts to eliminate HCV as a global public health threat will require strategies to enhance HCV testing and diagnosis globally, including the development of assays for rapid detection of HCV RNA.” – by Joe Green

Disclosures: Lamoury reports that he has received travel and accommodation support from Cepheid. Please see the study for all other authors’ relevant financial disclosures.

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