Utility of hepatitis C viral load monitoring on direct-acting antiviral therapy.

BACKGROUND Hepatitis C virus (HCV) RNA loads serve as predictors of treatment response during interferon-based therapy. We evaluated the predictive ability of HCV RNA levels at end of treatment (EOT) for sustained virologic response (SVR12) during interferon-sparing direct-acting antiviral therapies. METHODS HCV genotype 1-infected, treatment-naive patients were treated with sofosbuvir and ribavirin for 24 weeks (n = 55), sofosbuvir and ledipasvir for 12 weeks (n = 20), sofosbuvir, ledipasvir, and GS-9669 for 6 weeks (n = 20), or sofosbuvir, ledipasvir, and GS-9451 for 6 weeks (n = 19). Measurements of HCV RNA were performed using the Roche COBAS TaqMan HCV test and the Abbott RealTime HCV assay. Positive predictive value (PPV) and negative predictive value (NPV) of HCV RNA less than the lower limit of quantification (<LLOQ) at EOT for SVR12 were calculated. RESULTS All 55 patients treated with sofosbuvir and ribavirin had HCV RNA <LLOQ at EOT by the Roche and Abbott assays, but only 38 achieved SVR12 (PPV, 69%). Among patients treated with sofosbuvir and ledipasvir with or without GS-9669 or GS-9451, 100% (59/59) had HCV RNA <LLOQ by the Roche assay and 1 relapsed (PPV, 98%). By the Abbott assay, 90% (53/59) had HCV RNA <LLOQ, of whom 1 patient relapsed (PPV, 98%). Notably, 6 patients with HCV RNA ≥LLOQ at EOT (range, 14-64 IU/mL) achieved SVR12 (NPV, 0%). Quantifiable HCV RNA (range, 15-57 IU/mL) was measured 2 weeks posttreatment in 4 individuals, and 4 weeks posttreatment in 1 patient (14 IU/mL). CONCLUSIONS Contrary to past experience with interferon-containing treatments, low levels of quantifiable HCV RNA at EOT do not preclude treatment success.