AIMS - The Adherence to Refills and Medications Scale (ARMS) has been associated with objective measures of adherence and may address limitations of existing self-report measures of diabetes medication adherence. We modified the ARMS to specify adherence to diabetes medicines (ARMS-D), examined its psychometric properties, and compared its predictive validity with HbA1C against the most widely used self-report measure of diabetes medication adherence, the Summary of Diabetes Self-Care Activities medications subscale (SDSCA-MS). We also examined measurement differences by age (<65 vs. ≥65 years) and insulin status.
METHODS - We administered self-report measures to 314 adult outpatients prescribed medications for type 2 diabetes and collected point-of-care HbA1C.
RESULTS - One of the 12-item ARMS-D items was identified as less relevant to adherence to diabetes medications and removed. The 11-item ARMS-D had good internal consistency reliability (α=0.86), maintained its factor structure, and had convergent validity with the SDSCA-MS (rho=-0.52, p<0.001). Both the ARMS-D (β=0.16, p<0.01) and the SDSCA-MS (β=-0.12, p<0.05) independently predicted HbA1C after adjusting for covariates, but this association did not hold among participants ≥65 years in subgroup analyses. There were no differences in ARMS-D or SDSCA-MS scores by insulin status, but participants on insulin reported more problems with adherence on two ARMS-D items (i.e., feeling sick and medicine costs).
CONCLUSIONS - The ARMS-D is a reliable and valid measure of diabetes medication adherence, and is more predictive of HbA1C than the SDSCA-MS, but takes more time to administer. The ARMS-D also identifies barriers to adherence, which may be useful in research and clinical practice.
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