Predictors of very low adherence with medications for osteoporosis: towards development of a clinical prediction rule

Summary We developed a clinical prediction rule score to predict medication non-adherence for women prescribed osteoporosis treatment. When combined into a summative score, 62% with seven or more points on the score demonstrated very low adherence. This compares with 17% subjects with fewer than seven points (c-statistic=0.74). Introduction Medication non-adherence is extremely common for osteoporosis; however, no clear methods exist for identifying patients at risk of this behavior. We developed a clinical prediction rule to predict medication non-adherence for women prescribed osteoporosis treatment. Methods Women undergoing bone mineral density testing and fulfilling WHO criteria for osteoporosis were invited to complete a questionnaire and then followed for 1 year. Adjusted logistic regression models were examined to identify variables associated with very low adherence (medication possession ratio <20%). The weighted variables, based on the logistic regression, were summed, and the score was compared with the proportion of subjects with very low adherence. Results One hundred forty two women participated in the questionnaire and were prescribed an osteoporosis medication. After 1 year, 36% (n=50) had very low adherence. Variables associated with very low adherence included prior non-adherence with chronic medications, agreement that side effects are concerning, agreement that she is taking too many medications, lack of agreement that osteoporosis is a worry, lack of agreement that a fracture will cause disability, lack of agreement that medications help her stay active, and frequent use of alcohol. When combined into a summative score, 36 of the 58 subjects (62%) with seven or more points on the score demonstrated very low adherence. This compares with 14 of the 84 (17%) subjects with fewer than seven points (c-statistic=0.74). Conclusion We developed a brief clinical prediction rule that was able to discriminate between women likely (and unlikely) to experience very low adherence with osteoporosis medications.