Predictive Validity of Self-Reported Measures of Adherence to Noninsulin Antidiabetes Medication against Control of Glycated Hemoglobin Levels

Abstract

Objective: To assess and compare the predictive validity of 4 self-reported adherence measures.

Methods: A convenience sample of 153 patients with type 2 diabetes completed a self-report with 4 items (SR-4) and a French version of the Morisky Medication Adherence Scale with 8 items (MMAS-8), reported the proportion of pills missed, and answered a single-item scale regarding their antidiabetes drug treatments. They also provided measures of glycated hemoglobin (A1C) taken between 3 and 6 months after the adherence measurements. We examined the relationship between self-reported adherence and glycemic control using the area under the receiver operating characteristics curve (AUC) and linear regression analyses.

Results: AUCs were 0.51, 0.52, 0.53 and 0.52 for the SR-4, MMAS-8, self-reported proportion of pills missed and single-item scale, respectively. AUCs stratified according to median duration of diabetes ranged from 0.55 to 0.63. Based on linear regression analyses adjusted for diabetes duration, the association measured in the total sample between adherence measures and A1C levels was not statistically significant. When regression analyses were performed among participants with A1C levels ≥7% only, SR-4, MMAS-8 and the single-item scale scores were significantly associated with A1C levels, and beta coefficients were associated with a 1-unit increase in adherence scores of -0.46, -0.20 and 0.38, respectively.

Conclusion: The results support the predictive validity of all measures except the self-reported proportion of missed pills.

Keywords: autodéclaration; diabète de type 2; glycemic control (A1C); maîtrise de la glycémie (A1c); medication adherence; noninsulin antidiabetic treatment; observance du traitement; predictive validity; self-report; traitement antidiabétique non insulinique; type 2 diabetes; validité prédictive.