Implications of HCV RNA level at week 4 of direct antiviral treatments for hepatitis C.

We aimed to determine whether the HCV viral load after four weeks of treatment (W4VL) with direct-acting antiviral agents (DAAs) predicts sustained virologic response (SVR) in a real-world clinical setting. We identified 21 095 patients who initiated DAA-based antiviral treatment in the national Veterans Affairs (VA) healthcare system from 01/01/2014 to 06/30/2015. Week 4 viral load was categorized as undetectable, detectable below quantification (DBQ), detectable above quantification (DAQ) with viral load ≤42 IU/mL and DAQ with viral load >42 IU/mL. Week 4 viral load was undetectable in 36.1%, detectable below quantification in 45.6%, DAQ ≤42 in 9.3%, DAQ >42 in 9.1%. Detectable above quantification was much more common and undetectable week 4 viral load much less common when tested with the Abbott RealTime HCV assay vs the Roche COBAS AmpliPrep/COBAS TaqMan Version 2 assay. Compared to patients with undetectable week 4 viral load (SVR=93.5%), those with detectable below quantification (SVR=91.8%, adjusted odds ratio [AOR] 0.79, P-value=.001), DAQ ≤42 (SVR=90.0%, AOR 0.63, P-value<.001) and DAQ >42 (SVR=86.2%, AOR 0.52, P-value<.001) had progressively lower likelihood of achieving SVR after adjusting for baseline characteristics and treatment duration. Among genotype 1-infected patients who were potentially eligible for 8-week sofosbuvir/ledipasvir monotherapy, we did not find evidence that treatment for 12 weeks instead of 8 weeks was associated with higher SVR, even among those with detectable above quantification. In summary, DBQ and DAQ W4VL are very common in real-world practice, contrary to what was reported in clinical trials, and strongly predict reduced SVR across genotypes and clinically relevant patient subgroups. Whether and how week 4 viral load results should influence treatment decisions requires further study.