Review of Adherence Measures for use in Phase Iv Studies and Recommendations for a new Standardized Generic Measure.

1. The definition of adherence: The WHO (2003) defines adherence as the extent to which a person’s behaviour corresponds with recommendations from a health care provider. This definition implies active, voluntary, and collaborative patient involvement. However, within most clinical trials, a participant is expected to passively follow a medication regimen. 2. A protocol-driven environment: A clinical trial is strictly driven and governed by a protocol. Titration, medication holidays, and variable dosing are not allowed by virtue of the study. However, they are common strategies in clinical practice to improve adherence. 3. A self-selecting population: The population who agrees to participate in a clinical trial is unusually motivated, do not have strong treatment preferences , and fit (often times) narrowly-stated inclusion criteria. 4. The impact on other endpoints: Adherence data alone is potentially interesting but is of little use in the absence of reasons for non-adherence which provide context and inform strategies for improvement. Adherence-related factors can rarely be comprehensively understood within a clinical trial environment without impacting on the primary objectives of the study.