Patient adherence: a blind spot in cost-effectiveness analyses?

Despite evidence that medication adherence can influence cost-effectiveness analysis (CEA) results, the extent to which published CEAs include adherence has not been fully characterized.

To characterize inclusion of patient adherence in CEAs of self-administered medications and to examine whether industry sponsorship affects adherence inclusion, because adherence exclusion might overstate the interventions' cost-effectiveness.

Systematic review of the English-language medical literature published between 1998 and 2003 identified 177 original CEAs of self-administered medications.

Two trained readers independently abstracted data. Adherence inclusion was estimated overall and by study characteristics. Predictors of inclusion were assessed with chi2 tests and logistic regression.

Among 177 CEAs, 30.5% explicitly modeled adherence; of these, only half modeled adherence in both base-case and sensitivity analyses. Only 21% of studies performed sensitivity analysis on adherence; fewer than half of these provided sufficient information to determine the impact on results. Of the remaining 20 studies, 9 were sensitive to adherence. Adherence inclusion varied across clinical areas (P = .022). Only 30% of chronic anticoagulation studies, 52% of cardiovascular risk reduction studies, 38% of neuropsychiatric studies, and 32% of HIV antiretroviral studies considered suboptimal adherence. Among 128 CEAs that disclosed study sponsorship, adherence was included in 25.4% of industry-sponsored and 35.1% of non-industrysponsored studies (P = .17).

Few CEAs modeled suboptimal medication adherence. As CEAs are meant to model "real world" costs and effects of interventions, investigators would do well to explicitly consider medication adherence in the future.