title: Assessing Self-reported Medication Adherence in Inflammatory Bowel Disease: A Comparison of Tools.
abstract: Capturing (non)-adherence to medical prescriptions in patients with inflammatory bowel disease (IBD) is challenging. We aimed to compare 3 different tools to measure self-assessed medication adherence of patients with IBD.
  
  
  
  Adult patients with Crohn's disease and ulcerative colitis were prospectively followed. IBD-specific medication use was collected by 3-monthly questionnaires. At 2.5 years of follow-up, medication adherence was assessed using 3 tools: (1) the 8-item Morisky Medication Adherence Scale (MMAS-8), (2) the single question how well patients take their daily medication using a Visual Analogue Scale (VAS), and (3) the Forget Medicine scale (FM), assessing how often patients forget their medication. Cross-sectional agreement among measures was visualized with scatterplots and quantified with Spearman's rank correlations.
  
  
  
  In total, 913 patients with IBD were analyzed, 697 of whom received IBD-specific medication. High adherence on the MMAS-8 was consistent with high scores on the VAS and low scores on the FM. Disagreement between tools increased when patients were less adherent. A correlation of 0.44 was found between the MMAS-8 and VAS; -0.59 between the MMAS-8 and FM, and -0.55 between the VAS and FM (all P < 0.01). The VAS most optimally represented the quantitative variability of adherence, whereas the MMAS-8 and the FM might have resulted in overestimation or underestimation of adherence due to unequal differences in outcome possibilities.
  
  
  
  In patients with IBD, a VAS seems the most appropriate tool for quantifying medication adherence in clinical practice. The MMAS-8 may be used additionally to provide insight in specific reasons for non-adherence.
authors.affiliation: *Department of Gastroenterology and Hepatology, University Medical Center Utrecht, Utrecht, the Netherlands; †Department of Public Health, Healthcare Innovation and Medical Humanities, Julius Centre for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, the Netherlands; and ‡Department of Gastroenterology and Hepatology, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands.
authors.forename: Mirjam
authors.initials: M
authors.lastname: Severs
authors.forename: Peter N P A
authors.initials: PN
authors.lastname: Zuithoff
authors.forename: Marie-Josée J
authors.initials: MJ
authors.lastname: Mangen
authors.forename: Mirthe E
authors.initials: ME
authors.lastname: van der Valk
authors.forename: Peter D
authors.initials: PD
authors.lastname: Siersema
authors.forename: Herma H
authors.initials: HH
authors.lastname: Fidder
authors.forename: Bas
authors.initials: B
authors.lastname: Oldenburg
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D004651:Employment; D005260:Female; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D057566:Self Report; D011795:Surveys and Questionnaires; D064232:Visual Analog Scale; D016903:Drug Monitoring