Study: HCV week 4 viral load predicts DAA treatment response

The hepatitis C virus (HCV) viral load after four weeks of treatment with direct-acting antiviral (DAA) agents predicts sustained virologic response (SVR) in a real-world clinical setting, according to a new study.

“The results support the use of 8-week sofosbuvir/ledipasvir regimens in a selected subgroup of patients  with genotype 1 infection without cirrhosis who are treatment-naive and have a baseline viral load less than 6 million,” senior author George Ioannou, MD, associate professor of medicine at the University of Washington in Seattle, told Medical Economics.

The researchers published their results online October 12, 2017, in Journal of Viral Hepatitis.

They identified 21,095 patients who initiated DAA-based antiviral treatment in the national Veterans Affairs (VA) healthcare system from January 1, 2014, to June 30, 2015. Week 4 viral load was undetectable in 36.1% of patients, detectable below quantification in 45.6%, detectable above quantification with viral load up to 42 IU/mL in 9.3% and detectable above quantification with viral load above 42 IU/mL in 9.1%.

Those with detectable below quantification (SVR=91.8%), detectable above quantification up to 42 (SVR=90.0%) and detectable above quantification above 42 (SVR=86.2%) had progressively lower likelihood of achieving SVR after adjusting for baseline characteristics and treatment duration as compared to patients with undetectable week 4 viral load (SVR=93.5%).

“A positive week 4 viral load is much more common than we previously thought from what was reported in clinical trials, and is associated with failure to achieve SVR,” said Ioannou. “A surprising finding was that a positive week 4 viral load was so much more common with the Abbott than with the Roche assays. It is unclear whether this is due to a greater true-positive rate or a greater false-positive rate, or both.”

Next: Should viral loads affect treatment?

Week 4 viral loads categorized as detectable below quantification and detectable above quantification are common in the real world for several reasons. “One reason is that the assays used to measure viral load now in the VA are more sensitive than the assays that were used in the randomized controlled trials. Perhaps a second reason is that patients in clinical trials are highly selected to be very compliant with their medications and to have few risk factors for low response,” said Ioannou.

He noted that there was no strong evidence that week 4 viral loads should influence treatment decisions. “In particular, we did not find evidence that 8-week regimens should be extended to 12 weeks when the week 4 viral load is positive,” he said.

The results are generalizable because they represent the results from an entire, national healthcare system. “The VA healthcare system represents patients from all over the country, treated in all kinds of settings and by many different kinds of providers, as would be expected in the general population,” he said.

Ioannou recommended that primary care physician should still always test the hepatitis C viral load at week 4 into treatment. “It is still the only test we have for patient compliance. Data will continue to evolve as to how to best use the results,” he said.