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Utility of the Morisky Medication Adherence Scale in gout: a prospective study

Authors Tan CSL, Teng GG, Chong KJ, Cheung PP, Lim AYN, Wee HL, Santosa A

Received 13 August 2016

Accepted for publication 9 November 2016

Published 2 December 2016 Volume 2016:10 Pages 2449—2457

DOI https://doi.org/10.2147/PPA.S119719

Checked for plagiarism Yes

Review by Single-blind

Peer reviewers approved by Dr Akshita Wason

Peer reviewer comments 2

Editor who approved publication: Dr Johnny Chen

CSL Tan,1 GG Teng,1,2 KJ Chong,2 PP Cheung,1,2 AYN Lim,1,2 HL Wee,3,4 A Santosa1,2

1University Medicine Cluster, Division of Rheumatology, National University Health System, 2Department of Medicine, Yong Loo Lin School of Medicine, 3Department of Pharmacy, Faculty of Science, 4Saw Swee Hock School of Public Health, National University of Singapore, Singapore

Background: The outcomes of any chronic illness often depend on patients’ adherence with their treatment. A tool is lacking to assess adherence in gout that is standardized, allows real-time feedback, and is easy to understand.
Objective: We set out to evaluate the utility of the 8-item Morisky Medication Adherence Scale (MMAS-8) in monitoring medication adherence in a multiethnic Asian gout cohort on urate-lowering therapy (ULT).
Methods: This cohort study recruited patients with gout where baseline and 6-monthly clinical data, self-report of adherence, and health status by Gout Impact Scale (GIS) and EuroQoL-5 dimension 3 levels were collected. Those who received at least 9 months of ULT were analyzed. Convergent and construct validities of MMAS-8 were evaluated against medication possession ratio (MPR) and known groups, clinical outcomes, and patient-reported outcomes. Internal consistency and test–retest reliability were assessed using Cronbach’s alpha and intraclass correlation coefficient (ICC), respectively.
Results: Of 91 patients, 92.3% were male, 72.5% Chinese with mean age 53.5 years. MMAS-8 (mean 6.17) and MPR (mean 96.3%) were poorly correlated (r=0.069, P=0.521). MMAS-8 did not differ between those who did or did not achieve target serum urate (SU) <360 µmol/L (P=0.852); or among those whose SU improved, stagnated, or worsened during follow-up (P=0.777). Adherence was associated with age (β=0.256, P=0.015) and education level (P=0.011) but not comorbidities, polypharmacy, or flare frequency. Concerns for medication side effects and anxiety or depression were associated with lower MMAS-8 (P<0.005). Internal consistency was acceptable (α=0.725) and test–retest reliability was satisfactory (ICC =0.70, 95% confidence interval [CI] 0.36–0.88).
Conclusion: MMAS-8 had limited construct validity in assessing medication adherence to ULT in our gout patients. Nevertheless, it identified patients bothered or worried about ULT side effects, and those with underlying anxiety or depression, for whom targeted education and coping support may be useful.

Keywords: gout, 8-item Morisky Medication Adherence Scale, MMAS-8, serum urate, urate-lowering therapy, Singapore

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