title: Nonadherence to disease modifying antirheumatic drugs in the first year after diagnosis: comparing three adherence measures in early arthritis patients.
abstract: OBJECTIVE
  The aim of this study was to compare three measurement methods for non-adherence to DMARDs in early arthritis patients: the Compliance Questionnaire Rheumatology (CQR), the intracellular uptake of MTX in the form of MTX-polyglutamates (MTX-PGs) and electronic measurement with Medication Event Monitoring Systems (MEMS).
  
  
  METHODS
  DMARD naïve early arthritis patients were included in an ongoing cohort study. MEMS were used to measure adherence continuously, while every 3 months MTX-PGs were collected together with the CQR. The associations between the measures were estimated with Spearman rank correlations. Sensitivity and specificity of the CQR against a MEMS cut-off was compared at 3, 6, 9 and 12 months. The same applied to MTX-PGs against a MEMS cut-off and MTX-PGs against a CQR cut-off. For the association between MEMS, the CQR and MTX-PGs, a multilevel linear regression model was performed with age, gender, weeks of treatment and MTX dosage as covariates.
  
  
  RESULTS
  We included 206 patients. Non-adherence measured with MEMS varied over time and between DMARDs. The CQR score was not associated with MEMS non-adherence at 3, 9 and 12 months. At 9 months, MTX-PGs was associated with MEMS non-adherence, as well as with the CQR. All correlations were below 0.30.
  
  
  CONCLUSIONS
  Associations between the three measures are weak. Explanations are individual differences in the uptake of MTX, and little variance in adherence between patients. Moreover, the measurement domains differ: perceptions (CQR), behaviour (MEMS) and pharmacokinetics (MTX).
authors.affiliation: Department of Rheumatology a.pasma@erasmusmc.nl.
authors.forename: Annelieke
authors.initials: A
authors.lastname: Pasma
authors.affiliation: Department of Rheumatology.
authors.forename: Ethan
authors.initials: E
authors.lastname: den Boer
authors.affiliation: Department of Psychiatry, Section Medical Psychology and Psychotherapy, Erasmus Medical Center, University Medical Center Rotterdam.
authors.forename: Adriaan
authors.initials: A
authors.lastname: van 't Spijker
authors.affiliation: Department of Psychiatry, Section Medical Psychology and Psychotherapy, Erasmus Medical Center, University Medical Center Rotterdam.
authors.forename: Reininer
authors.initials: R
authors.lastname: Timman
authors.affiliation: Department of Pharmacy, Sint Maartenskliniek, Nijmegen, the Netherlands.
authors.forename: Bart
authors.initials: B
authors.lastname: van den Bemt
authors.affiliation: Department of Psychiatry, Section Medical Psychology and Psychotherapy, Erasmus Medical Center, University Medical Center Rotterdam.
authors.forename: Jan J V
authors.initials: JJ
authors.lastname: Busschbach
authors.affiliation: Department of Rheumatology.
authors.forename: Johanna M W
authors.initials: JM
authors.lastname: Hazes
mesh_terms: D018501:Antirheumatic Agents / Q000493:pharmacokinetics / Q000627:therapeutic use*; D001172:Arthritis, Rheumatoid / Q000188:drug therapy*; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D008297:Male; D055118:Medication Adherence; D008727:Methotrexate / Q000493:pharmacokinetics / Q000627:therapeutic use*; D008875:Middle Aged
chemical_list: D018501:Antirheumatic Agents; D008727:Methotrexate
keywords: DMARDs; early arthritis; non-adherence