The Parkinson's Disease Activities of Daily Living, Interference, and Dependence Instrument.

BACKGROUND: Individuals with Parkinson's disease often experience periods of off time when their motor symptoms are poorly controlled, significantly impacting their lives. OBJECTIVES: To identify the consequences of motor fluctuations on day-to-day activities and areas of unmet treatment priority among individuals with moderate to advanced Parkinson's disease, to assess whether existing patient-reported outcome instruments adequately capture these consequences and priorities, and based on these evaluations, to adapt an existing or develop a new instrument. METHODS: The research was conducted in 2 stages: concept exploration and content confirmation. Concept exploration included direct input from individuals with Parkinson's disease representing the intended context of use via concept elicitation interviews. Content confirmation and item refinement was achieved through 5 rounds of cognitive debriefing. Final rounds of cognitive debriefing also included usability testing of the draft instrument for electronic data capture. RESULTS: Concept elicitation interviews were conducted among 29 individuals with Parkinson's disease (55% male; mean age 60.8 years). Concept saturation was achieved quickly with more than 90% of concepts identified by the end of the 16th interview. None of the existing outcome instruments were found to be fit for purpose in the intended context of use; therefore, a new instrument was developed. After 5 rounds, cognitive debriefing participants indicated clear and consistent interpretation of the items. CONCLUSIONS: Evidence from this study supports the content validity of the Parkinson's Disease Activities of Daily Living, Interference and Dependence Instrument as the basis of a clinical trial endpoint for capturing priority treatment benefit outcomes to individuals with moderate to advanced Parkinson's disease experiencing motor fluctuations.