Self-reported adherence versus pill count in Parkinson's disease: the NET-PD experience.

Purpose: To compare the Morisky medication adherence questionnaire to pill counts as measures of adherence in the NET-PD futility clinical trials.

Background: Like in other chronic diseases, non-adherence with medications occurs in Parkinson's disease (PD), although nonadherence has not been of significant concern in most PD clinical trials. The most common approach to assessment is to do a pill count at each visit. The simple, 4-question Morisky medication adherence questionnaire may provide an alternative approach to monitoring treatment adherence in PD.

Methods: Adherence data from two NET-PD Phase II clinical trials enrolling a total of 413 participants were analyzed. The association between demographic and clinical characteristics and adherence was explored.

Results: Ninety-percent of participants took 80% or more of the study drug. However, the Morisky medication adherence questionnaires showed 56% report high and 44% report medium adherence. Agreement between the two measures is fair (ICC = 0.40).

Conclusions: Overall adherence as assessed by pill count appears high. The Morisky medication adherence questionnaire may be useful in PD clinical trials, since it is moderately correlated to pill count and may be more sensitive to nonadherence.