von Willebrand factor antigen: a novel on-treatment predictor of response to antiviral therapy in chronic hepatitis C genotypes 1 and 4

Background: Levels of von Willebrand factor antigen (vWF-Ag) increase during combination antiviral therapy of chronic hepatitis C (CHC). The present study investigates the association between these changes in vWF-Ag levels and response to treatment. Methods: Changes in levels of vWF-Ag on antiviral combination treatment in 184 patients with CHC genotype 1 or 4 infections were measured prospectively and effect on response was studied. Results: High on-treatment levels of vWF-Ag were associated with relapse (P<0.01) and low on-treatment levels with sustained virological response (SVR). Receiver operating characteristic curve analysis showed that vWF-Ag levels of <300% at week 12 of therapy have a positive predictive value (PPV) of 78% for SVR. In early virological response (EVR) patients, the PPV of vWF-Ag levels <300% at week 12 was 74%. An even higher PPV of 88% in complete EVRs (undetectable HCV RNA at week 12) was observed for the same cutoff value at week 12. Conclusions: On-treatment levels of vWF-Ag can be utilized as an additional predictive marker for response to antiviral therapy. This is especially relevant in EVR patients because EVR alone only has a PPV of 58-72% on SVR, which increased to 74%, when factoring in vWF-Ag levels <300% at week 12, and to 88% in complete EVRs; therefore, measurement of vWF-Ag levels at week 12 is helpful. EVR patients that are above the cutoff values for vWF-Ag that make SVR very probable might profit from an extension of therapy to 72 weeks.