The combination of pegylated interferon and ribavirin (PEG-IFN/RBV) is the standard of care treatment for HCV for both mono- and HIV co-infected patients. The side effects of HCV treatment (e.g., anemia, neutropenia, depression, flu-like symptoms) often result in dose reductions (30-40% of patients) and early treatment discontinuation (1
). While the 80/80/80 rule (continued prescription of at least 80% of interferon doses and 80% of ribavirin doses for at least 80% of the planned treatment duration) is widely referred to as the gold standard of HCV treatment adherence (2
), this standard refers to dose reductions and premature discontinuation of treatment only, not to patient dose-taking adherence.
Rates of treatment uptake are low (4
), particularly among HIV co-infected patients (~5-10%) (5
); this is in part due to limited treatment efficacy, but also because of anticipated difficulties with adherence as a result of common treatment toxicities. Rates of HCV virologic response have been found to be lower in HIV co-infected patients (27-40%) (7
) than HCV mono-infected patients (54-56%) (1
). These findings may in part be due to the fact that lower doses of ribavirin were generally used in the main co-infection trials as compared to the mono-infection trials (11
). There is evidence that suboptimal dosing and dose reductions in HCV therapy, particularly of ribavirin, are associated with lower rates of HCV virologic response (2
). These observations suggest that missed doses of PEG-IFN and RBV are also likely to negatively impact HCV virologic response.
To date only two published studies have reported on patient dose-taking adherence to HCV therapy (13
). In an observational clinic cohort of HIV-co-infected patients, Fumaz and colleagues (13
) found that over 98% of patients self-reported taking all doses of pegylated interferon and ribavirin in the prior 2 weeks at weeks 12, 24, and 48. In a clinical trial sample of HCV mono-infected subjects, Smith and colleagues (14
) found that at least 95% of subjects self-reported taking all doses of pegylated interferon in the prior 4 weeks at weeks 4, 12, 24, 36 and 48. They found that the percent of patients who self-reported taking all doses of ribavirin in the prior 4 days decreased over time (91% at 4 weeks, 85% at 12 weeks, 83% at 24 weeks, 76% at 36 weeks, 75% at 48 weeks). Self-report measures have been found to overestimate adherence compared to objective measures such as electronic monitoring (15
). Studies of HIV antiretroviral adherence have demonstrated mean adherence rates ranging from 80-95% when measured by self-report, and rates as low as 55-65% when measured by electronic monitoring (15
). Consistent with these findings, Smith and colleagues (14
) found lower rates of adherence to pegylated interferon and ribavirin as measured by MEMS as compared to self-report in their clinical trial sample.
To gain a greater understanding of the prevalence of missed doses of PEG-IFN/RBV, and correlates of nonadherence, we conducted a cross-sectional survey of dose-taking adherence to PEG-IFN/RBV among mono- and HIV co-infected patients currently on PEG-IFN/RBV for at least 4 weeks. All patients who had completed at least 4 weeks of HCV treatment were eligible to complete the survey.