Wednesday, June 7, 2017

Hepatitis C - Week 4 viral load and SVR

Implications of HCV RNA level at week 4 of direct antiviral treatments for Hepatitis C
Kay Johnson MD, MPH1, Pamela K. Green PhD2, George N. Ioannou BMBCh MS1,2,3.

DBQ = Detectable below quantification
DAQ ≤42 = Detectable above quantification with an HCV RNA level ≤42 IU/mL
DAQ>42 = Detectable above quantification with an HCV RNA level > 42 IU/mL
W4VL = week 4 viral load (the HCV RNA viral load 4 weeks after initiation of antiviral treatment)

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, detectable above quantification with viral load ≤42 IU/mL and detectable above quantification with viral load > 42 IU/mL. Week 4viral load was undetectable in 36.1%, detectable below quantification in 45.6%, detectable above quantification ≤42 in 9.3%, detectable above quantification >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 versus the Roche COBAS AmpliPrep/COBASTaqMan 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=0.001), detectable above quantification ≤42 (SVR=90.0%, AOR 0.63, p-value<0.001) and detectable above quantification >42 (SVR=86.2%, AOR 0.52, p-value<0.001) 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
detectable below quantification  and detectable above quantification  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.

Response-guided therapy

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