Measurements of medication adherence in diabetic patients with poorly controlled HbA(1c)

Diabet Med. 2010 Feb;27(2):210-6. doi: 10.1111/j.1464-5491.2009.02898.x.

Abstract

Aims: To assess pharmacy claims and self-report data as measures of medication adherence and to describe baseline characteristics of subjects in the Improving Diabetes Outcomes Study.

Methods: Multi-ethnic, lower-income, insured adults (n = 526) in New York City with Type 2 diabetes were enrolled in a randomized, controlled, behavioural intervention study delivered by telephone. Baseline data were examined, including glycated haemoglobin (HbA(1c)), objective measures of diabetes medication adherence [claims data medication possession ratio (MPR)], and two self-report measures [Morisky Medication-taking Scale and the medication-taking item of the Summary of Diabetes Self-Care Activities (SDSCA)]. Associations of highest tertile HbA(1c) (>or= 9.3%) with lowest tertile MPR (< 42%) were assessed with logistic regression models adjusting for potential confounders. Subset analyses were performed based on assessment of potential interaction.

Results: Participants (mean +/- sd age 56 +/- 7 years) had median (interquartile range) HbA(1c) 8.6% (8.0-10.0). Correlations of baseline MPR with Morisky score and SDSCA medication-taking item were strongly significant (both rho = 0.21, P < 0.001). Lowest MPR was significantly (P = 0.008) associated with highest HbA(1c) in the group as a whole and among the subset taking two or more oral glucose-lowering agents (OGLA) (P = 0.002), but not among the subset taking only one (P = 0.83). Self-report adherence measures were not significantly associated with HbA(1c) in either the whole group or either subset.

Conclusions: These results support the validity of MPR as an adherence measure for OGLA among insured diabetes patients with poorly controlled HbA(1c), especially those taking two or more OGLA.

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural

MeSH terms

  • Diabetes Mellitus, Type 2 / drug therapy*
  • Female
  • Glycated Hemoglobin A / analysis*
  • Humans
  • Hypoglycemic Agents / therapeutic use*
  • Logistic Models
  • Male
  • Medication Adherence / statistics & numerical data*
  • Middle Aged
  • New York City
  • Pharmacy Service, Hospital / statistics & numerical data
  • Reproducibility of Results
  • Surveys and Questionnaires

Substances

  • Glycated Hemoglobin A
  • Hypoglycemic Agents