The ARMS-D out performs the SDSCA, but both are reliable, valid, and predict glycemic control

AimsThe 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.MethodsWe administered self-report measures to 314 adult outpatients prescribed medications for type 2 diabetes and collected point-of-care HbA1C.ResultsOne 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).ConclusionsThe 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.