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Point-of-care HCV Assays: A Turning Point for Decentralized Diagnosis
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Novel point-of-care hepatitis C tests have advanced the potential for same-day viral diagnosis, which could significantly contribute to global elimination efforts by reaching difficult-to-engage populations such as homeless individuals, people who inject drugs, and individuals in low- or middle-income settings.
Data from recent studies showed several current point-of-care tests are feasible for primary care physicians and clinicians, acceptable if not preferred by patients, have similar diagnostic accuracy compared with other verified tests such as nucleic acid testing, and are particularly suitable for screening high-risk populations and people in remote locations.
“Assay development and regulatory approval are the most important steps in order to develop point-of-care assays for HCV,” Andrew H. Talal, MD, MPH, from the University at Buffalo, New York, told Healio Gastroenterology and Liver Disease. Talal noted that there is still only a limited option of commercial HCV antibody tests, which can be problematic as patients require both anti-HCV antibody screening and follow-up HCV RNA testing.
Talal added that while vibration controlled transient elastography (VCTE) may be an alternative option to screen for hepatitis C via fibrosis staging in primary care settings, it is not optimal.
“Although VCTE may be feasible to do in clinics, there are several logistical issues that are required such as adequate space, staff support and the time to do the test,” Talal said. “It can take up to 30 minutes, on occasion, to obtain proper measurement.”
New Technology
Point-of-care tests typically consist of immunoassays that provide qualitative and quantitative determination of various infection markers, such as antigens and antibodies, within a limited amount of time. While many tests use venous puncture to collect whole blood, serum or plasma, researchers have focused on alternatives such as fingerstick or oral fluid testing.
Compared with traditional hepatitis virological tests, the benefit of point-of-care diagnostics is their use in patient care sites such as outpatient clinics, intensive care units, emergency departments and medical laboratories. Additionally, certain low- and middle-income countries have made use of point-of-care tests in blood banks.
The current point-of-care HCV tests available or currently being researched include rapid diagnostic tests for antibodies, nonimmunologic tests, and dried blood spot tests.
Rapid Diagnostic Tests
Rapid diagnostic tests are designed to capture specified antigens or antibodies. According to the World Health Organization “ASSURED” criteria, rapid diagnostic tests must be easy to use with minimal training, have a shelf life of at least 1 to 2 years at ambient temperature, and a limited need for instrumentation.
At the recent International Liver Congress in Paris, Bridget Williams, MD, public health registrar from the Burnet Institute in Melbourne, Australia, presented data on a combination of point-of-care HCV antibody and RNA testing used in patients with a history of injection drug use. Patients who underwent the 20-minute OraQuick HCV antibody mouth swab test (OraSure Technologies) and received positive results were offered to undergo venipuncture for Xpert HCV Viral Load assay (Cepheid), which took 105 minutes to confirm HCV RNA.
According to the presentation, patients received same-day results on site during their return to the clinic or via phone or text message.
Williams showed significant follow-through, as 93% of patients underwent point-of-care HCV RNA testing and 60% of the 67 patients who did not initially undergo RNA testing returned for follow-up. Additionally, 85% of study participants preferred point-of-care testing over standard HCV testing processes.
“Many participants had received their diagnosis of hepatitis C many years ago but had not sought out care, despite the new, very effective treatments being available in Australia,” Williams said during her presentation. “This suggests that the use of point-of-care tests could serve to re-engage patients into care.”
Nonimmunological Tests
Nonimmunological or nucleic acid point-of-care tests detect and may quantify pathogen nucleic acids at early development stages.
The Xpert HCV Viral Load test (Cepheid) in conjunction with Cepheid’s GeneXpert Omni device displayed comparable performance with commercially available HCV RNA assays in a recent study, with a limit detection of 40 IU/mL, lower limit quantification of 100 IU/mL (2 log 10 IU/mL) and an upper limit of linear quantification of 100,000,000 IU/mL (8 log 10 IU/mL). The Xpert HCV Viral Load test received CE marking and WHO prequalification.
A study conducted by François M.J. Lamoury, senior research officer at the University of New South Wales Kirby Institute in Sydney, Australia, and colleagues showed that the new Xpert HCV VL FS assay (Cepheid) — a redesigned version of the Xpert HCV Viral Load assay — can test a 100 µL sample of capillary blood. According to Lamoury and colleagues, both the previous assay and the redesigned version had sensitivity and specificity of 100% with a 95% confidence interval minimum no lower than 93.9.
The Genedrive rapid thermocycler (Genedrive Diagnostics) permits nucleic acid amplification testing on plasma or serum samples followed by reverse transcription reaction to generate complementary DNA from target HCV RNA. Alba Llibre, MD, from the Institut Pasteur, France, and colleagues were able to obtain results from 97.2% of samples during the first attempt and 61.5% of retested samples with a sensitivity of 98.6% and specificity of 100%.
The Genedrive also demonstrated 100% sensitivity and specificity compared with the m2000 RealTime System from Abbott.
Another recent device is the Alere q rapid molecular point-of-care platform (Abbott, Chicago, IL): a battery-powered, fully automated, cartridge-based assay that does not require sample extraction and received CE marking for HIV RNA detection. Currently, an HCV RNA assay using small blood samples is under development for the Alere q.
“Abbott Diagnostics recent purchase of Alere is expected to move point-of-care testing forward as Abbott enters this space,” Talal said to Healio Gastroenterology and Liver Disease.
Dried Blood-spot Tests
Dried blood-spot tests for infectious diseases come with several benefits and limitations. The procedure is simple — collection of a few drops of blood drawn by a lancet on absorbent filter paper — and can be shipped as nonhazardous materials to reference laboratories for serological and molecular testing. Additionally, they can be prepared by health care practitioners with limited training.
However, dried blood spot tests have reduced analytical sensitivity compared with fresh plasma or serum and results may vary depending on quality and volume of blood, quality of filter paper, and extraction and detection methods. Still, dried blood spot tests offer a unique opportunity to reach undiagnosed patients, particularly in remote locations.
While there are currently no commercial HCV RNA assays approved for use with whole blood from dried blood spot tests, real-time polymerase chain reaction assays are under clinical review.
One such assay, the m2000 RealTime System, has shown significant potential for point-of-care diagnosis. In a study using dried blood spot testing among individuals in the Democratic Republic of the Congo, Jonathan B. Parr, MD, MPH, from the University of North Carolina School of Medicine, and colleagues found that the m2000 accurately detected HCV RNA.
“Hepatitis C infections remain underdiagnosed and undertreated in marginalized populations, despite the development of well-tolerated, curative antiviral medications,” Parr told Healio Gastroenterology and Liver Disease. “We validated a simple testing approach that requires collection of only a single drop of blood on filter paper. This approach is easily implemented using existing laboratory infrastructure in large surveys, including those in resource-limited settings.”
Looking Ahead
While researchers such as Jason Grebely, PhD, from the Kirby Institute, University of New South Wales, Sydney, have noted that up-front costs for assay-reading instruments and costs per assay are likely to be more expensive than standard anti-HCV testing, the point-of-care approach could be particularly suitable for high-risk populations and may be useful in primary care clinics or opioid treatment centers.
In a review of point-of-care testing for viral hepatitis, Stéphane Chevaliez, PharmD, PhD, and Jean-Michel Pawlotsky, MD, PhD, from the National Reference Center for Viral Hepatitis B, C and D, in France advocated for updated testing policies and noted the importance of overcoming challenges related to point-of-care implementation.
“Point-of-care tests offer substantial benefits for the management of patients with viral hepatitis, by shortening the time to results and by making the test available at the bedside or at remote care centers,” Chevaliez and Pawlotsky wrote. “The next technical challenge is the development of point-of-care tests that simultaneously measure multiple analytes in the same cartridge. Better standardization and optimization of intrinsic performance are also needed.”
As knowledge regarding the health risks related to hepatitis C increases among both physicians and patients, decentralized HCV testing with quick turnaround could make a significant difference in primary care settings, especially if both antibody and RNA tests can be paired for confirmative diagnoses. – by Talitha Bennett and Marley Ghizzone
- References:
- Chevaliez S, et al. J Hepatol. 2018;doi:10.1016/j.jhep.2018.06.017.
- Grebely J, et al. Lancet Gastroenterol Hepatol. 2017;doi:10.1016/S2468-1253(17)30075-4.
- Lamoury FMJ, et al. J Infect Dis. 2018;doi:10.1093/infdis/jiy114.
- Llibre A, et al. Gut. 2018;doi:10.1136/gutjnl-2017-315783.
- Parr JB, et al. Clin Infect Dis. 2017;doi:10.1093/cid/cix771.
- Williams B, et al. Abstract 405. Presented at: International Liver Congress; April 11-15, 2018; Paris.
- For more information:
- Andrew H. Talal, MD, MPH, can be reached at ahtalal@buffalo.edu.
- Jonathan B. Parr, MD, MPH, can be reached at jonathan_parr@med.unc.edu.
Disclosures: Talal reports financial connections with Abbott, AbbVie, Chronic Liver Disease Foundation, Conatus, Gilead, Intercept, Merck and Tobira. Parr reports no relevant financial disclosures.