Hepatitis C virus direct-acting antiviral nonadherence: Relationship to sustained virologic response and identification of at-risk patients.

Objectives: There is a dearth of literature on effects of nonadherence to hepatitis C virus (HCV) direct-acting antiviral (DAA) regimens; thus, the objective of our study was to assess the impact of adherence on sustained virologic response (SVR) and evaluate factors associated with nonadherence, such as race, psychiatric comorbidities, and therapy length.

Methods: We conducted a retrospective cohort study of patients completing DAA treatment between January 2014 and May 2016 within an interdisciplinary hepatology clinic. Adherence was defined a priori as 95% or greater of DAA doses taken within the prescribed treatment period. Post hoc analyses were done with adherence thresholds ≥ 90%, ≥ 85%, and ≥ 80% and adherence as a continuous percentage. Patients lost to follow-up before completing therapy or that discontinued therapy early were excluded from analyses. The association between adherence and SVR rates was assessed using Fisher exact test (for adherence thresholds) and the Wilcoxon rank-sum test (for continuous adherence). Factors associated with adherence were assessed similarly using Fisher exact and Wilcoxon rank-sum tests and multivariable logistic regression.

Results: Overall adherence was high, with an average of 97.8% of DAA doses taken within the prescribed treatment period. Achievement of SVR was not significantly different in adherent and nonadherent patients, at an adherence threshold of 95% or greater (93.4% vs. 88.5%; P = 0.246) or any of the post hoc adherence thresholds (≥ 90% [93.3% vs. 84.0%; P = 0.098], ≥ 85% [92.8% vs. 91.7%; P = 0.601], ≥ 80% [92.9% vs. 80.0%; P = 0.315], or as a continuous percentage [P = 0.328]). Black patients were significantly more likely to be nonadherent to DAAs than non-black patients at each adherence threshold (P < 0.05). No other factors evaluated were associated with nonadherence.

Conclusion: A numerically higher but not statistically significant SVR failure rate was noted in nonadherent patients, although the gold standard definition for adherence remains to be established. Black patients may require additional adherence support.