Factors influencing adherence in Hepatitis-C infected patients: a systematic review

BACKGROUND: Adherence is a crucial point for the successful treatment of a hepatitis-C virus infection. Studies have shown that especially adherence to ribavirin is important. The objective of this systematic review was to identify factors that influence adherence in hepatitis-C infected patients taking regimes that containing ribavirin. METHODS: A systematic literature search was performed in Medline and Embase in March 2014 without limits for publication date. Titles and abstracts and in case of relevance, full-texts were screened according to predefined inclusion criteria. The risk of bias was assessed. Both process steps were carried out independently by two reviewers. Relevant data on study characteristics and results were extracted in standardized tables by one reviewer and checked by a second. Data were synthesized in a narrative way using a standardized procedure. RESULTS: Nine relevant studies were identified. The number of analyzed patients ranged between 12 and 5706 patients. The study quality was moderate. Especially the risk of bias regarding the measurement of influencing factors was mostly unclear. “Psychiatric disorders” (N = 5) and having to take “higher doses of ribavirin” (N = 3) showed a negative influence on adherence. In contrast, a “HIV co-infection” (N = 2) and the “hemoglobin level” (N = 2) were associated with a positive influence on adherence. Furthermore, there is the tendency that male patients are more adherent than female patients (N = 6). “Alcohol consumption” (N = 2), “education”, “employment status”, “ethnic group“,”hepatitis-C virus RNA” (N = 4), “genotype” (N = 5), “metavir activity” (N = 1) and “weight” (N = 3) showed mostly no effect on adherence. Although, some studies showed statistically significant results for “age”, “drug use” , “genotype”, “medication dose interferon“, and “treatment experience” the effect is unclear because effect directions were partly conflicting. The other factors were heterogeneous regarding the effect direction and/or statistical significance. CONCLUSION: There are some factors that seem to show an influence on adherence. However, due to the heterogeneity (e.g. patient characteristics, regimes, settings, countries) no general conclusions can be made. The results should rather be considered as indications for factors that can have an influence on adherence in hepatitis-C infected patients taking regimes that containing ribavirin.