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PURPOSE: Adherence is a major determinant of the therapeutic effectiveness of medications. Despite evidence that adherence can influence the results and conclusions of cost-utility analyses (CUAs), little is known about whether published studies consider it. Our objective was to examine the inclusion of patient adherence in CUAs of medications. Because the exclusion of adherence might overstate the cost-effectiveness of interventions, we also examined the relationship between pharamaceutical company sponsorship and adherence inclusion.
METHODS: A systematic review of the English-language literature published between 1998 and 2001 identified 294 original CUAs, including 98 pertaining to self-administered medications. Two trained readers independently abstracted detailed data on study methods and results, and completed a consensus form for each item, including an item on whether compliance or adherence to intervention was considered. We estimated rates of adherence inclusion overall and by study characteristics. Association between adherence inclusion and study sponsorship was assessed with a chi-square test.
RESULTS: Among the 98 CUAs of self-administered medications, 40% (n=39) considered patient adherence to therapy. Adherence was equally likely to be considered in CUAs of long-term versus short-term (< 1 month) drug therapy (39% vs. 44%, p=0.65). Inclusion of adherence varied across the most commonly studied clinical areas: 25% of chronic anticoagulation studies, 57% of cardiovascular risk reduction studies, 50% of neuropsychiatric studies, and 40% of HIV antiretroviral studies. Among the 70 CUAs in which study sponsorship was disclosed, 40% of pharmaceutical sponsored studies (n=40) and 50% of non-pharmaceutical sponsored studies (n=30) included adherence (difference non-significant).
CONCLUSIONS: Despite its potential importance, few CUAs incorporate medication adherence. As decision and cost-effectiveness analyses are meant to explicitly model 'real world' costs and effects of interventions, investigators would do well to explicitly consider medication adherence in future analyses.
See more of Poster Session - CEA: Methods and Applications; Health Services Research
See more of The 26th Annual Meeting of the Society for Medical Decision Making (October 17-20, 2004)