Reply to Harrington et al

To the Editor—Harrington et al raise 3 important points in a detailed analysis of pooled data from 12 registrational trials of interferon-free, direct-acting antiviral (DAA) therapies [1]. First, the authors point out that hepatitis C virus (HCV) RNA was detected at the end of treatment in only 0.3% (12/3671) of patients who achieved sustained virological response 12 (SVR12) in the larger trials compared to 29% (28/96) in our studies [2]. As suggested by Harrington et al, our use of the more sensitive Abbott RealTime HCV assay could have resulted in higher rates of detectable viremia. Conversely, using the Roche COBAS TaqMan HCV test v1.0, only 3.1% (3/96) of patients who achieved SVR12 in our studies had a detectable viral load at the end of therapy. These differences may also be a result of varying treatment durations among the trials: over one-third of our patients were treated for 6 weeks, whereas the majority of subjects from the pooled data were treated for 12–24 weeks. Longer durations of therapy may certainly result in higher rates of viral suppression by the end of treatment.