Validation of the transtheoretical model in medication compliance behavior
Cook, Christopher Lawrence
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Practical and theoretically derived interventions are needed to improve medication compliance with prescribed therapies. The Transtheoretical Model of Behavioral Change (TTM) has been applied to various health related behaviors. This research examined whether the TTM is applicable to medication compliance behavior. A medication compliance measure using the TTM constructs of stages of change, decisional balance, and self-efficacy was developed. The scale development process consisted of two pilot trial phases and a patient testing phase. Two pilot surveys were administered to community pharmacy populations of 159 and 70 subjects. Initial testing provided valuable information in item selection and reduction for the final survey. The pilot surveys demonstrated the stage of change construct to exist as a three-factor structure consisting of precontemplation, contemplation, and maintenance for medication compliance behavior. Analysis of these surveys also revealed complexities in the multiple- item stage of change measure providing support to the use of a single- item stage of change measure. The final survey form was tested using patients from 5 primary care physicians’ offices. Patients diagnosed with diabetes, hypothyroidism, hypercholesterolemia, hypertension, or being treated with hormone replacement therapy were asked to complete a survey consisting of demographic questions, the TTM construct measures, and three compliance measures. Pharmacy refill records were collected for participating subjects as a fourth measure of compliance. Moderate correlations ranging from 0.18 to 0.79 were found between the TTM- model constructs and the four compliance measures. Regression models demonstrated that a range 9.61% to 41.07% of the variance in medication compliance could be explained through the TTM-constructs. The study results support additional investigation of the TTM in medication compliance behavior.