title: Relationship between adherence to hepatitis C virus therapy and virologic outcomes: a cohort study.
abstract: BACKGROUND
  Adherence to therapy with pegylated interferon and ribavirin for hepatitis C virus (HCV) infection has been incompletely examined.
  
  
  OBJECTIVE
  To evaluate the relationship between adherence to HCV therapy and early and sustained virologic response, assess changes in adherence over time, and examine risk factors for nonadherence.
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  National Veterans Affairs Hepatitis C Clinical Case Registry.
  
  
  METHODS
  5706 HCV-infected patients (genotypes 1, 2, 3, or 4) with at least 1 prescription for both pegylated interferon and ribavirin between 2003 and 2006 and HCV RNA results before and after treatment initiation.
  
  
  METHODS
  Adherence was calculated over 12-week intervals by using pharmacy refill data. End points included early virologic response (decrease of ≥2 log(10) HCV RNA at 12 weeks) and sustained virologic response (undetectable HCV RNA 24 weeks after the end of treatment).
  
  
  RESULTS
  Early virologic response increased with higher levels of adherence to ribavirin therapy over the initial 12 weeks (patients with HCV genotype 1 or 4, 25 of 68 [37%] with ≤40% adherence vs. 1367 of 2187 [63%] with 91% to 100% adherence [P < 0.001]; patients with HCV genotype 2 or 3, 12 of 18 [67%] with ≤40% adherence vs. 651 of 713 [91%] with 91% to 100% adherence [P < 0.001]). Among patients with HCV genotype 1 or 4, sustained response increased with higher adherence to ribavirin therapy over the second, third, and fourth 12-week intervals. Results were similar for adherence to interferon therapy. Mean adherence to therapy with interferon and ribavirin decreased by 3.4 and 6.6 percentage points per 12-week interval, respectively (P for trend < 0.001 for each drug). Patients who received growth factors or thyroid medications during treatment had higher mean adherence to antiviral therapy.
  
  
  CONCLUSIONS
  This was an observational study without standardized timing for outcome measurements.
  
  
  CONCLUSIONS
  Early and sustained virologic responses increased with higher levels of adherence to interferon and ribavirin therapy. Adherence to therapy with both antivirals decreased over time, but more so for ribavirin.
authors.affiliation: University of Pennsylvania School of Medicine, Philadelphia, PA, USA. vincentl@mail.med.upenn.edu
authors.forename: Vincent
authors.initials: V
authors.lastname: Lo Re
authors.forename: Valerie
authors.initials: V
authors.lastname: Teal
authors.forename: A Russell
authors.initials: AR
authors.lastname: Localio
authors.forename: Valerianna K
authors.initials: VK
authors.lastname: Amorosa
authors.forename: David E
authors.initials: DE
authors.lastname: Kaplan
authors.forename: Robert
authors.initials: R
authors.lastname: Gross
mesh_terms: D000998:Antiviral Agents / Q000627:therapeutic use*; D004359:Drug Therapy, Combination; D005260:Female; D005838:Genotype; D016174:Hepacivirus / Q000235:genetics; D006526:Hepatitis C / Q000188:drug therapy* / Q000821:virology; D006801:Humans; D016898:Interferon-alpha / Q000627:therapeutic use*; D008297:Male; D055118:Medication Adherence; D008875:Middle Aged; D012367:RNA, Viral / Q000097:blood; D012189:Retrospective Studies; D012254:Ribavirin / Q000627:therapeutic use*; D012307:Risk Factors; D013997:Time Factors; D019562:Viral Load
chemical_list: D000998:Antiviral Agents; D016898:Interferon-alpha; D012367:RNA, Viral; D012254:Ribavirin