Pilot Assessment of the Effect of Optimism and Expectation on Dyskinesia Rating Scales in Parkinson's Disease Subjects Randomized to Placebo or Amantadine
MJFF Research Grant, 2009
The effects of placebo response in clinical and surgical interventions in PD have become increasingly recognized. Many factors have been associated with placebo response including disease and treatment related variables, as well as person-specific tendencies such as dispositional optimism, social conformity, expectations of outcome, and impulsivity. The influence of these subject-specific placebo response factors on rating scales used in PD research may be a major source of measurement bias that could provide misleading information regarding treatment studies.
Individual rating scales may be more susceptible to placebo effects than others. For example, it may be that rating scale based on patient self-report may be more influenced by patient optimism and expectations of positive outcomes than by investigator expectations. Conversely, scales that are completed by the investigator may be more susceptible to investigator expectations than to patient optimism or expectations of positive outcome. This pilot study will address the differential effects of patients optimism, social desirability, impulsivity and expectation of positive outcome along with investigator expectation of positive outcome on various dyskinesia rating scale used in a double-blind, placebo-controlled study of amantadine treatment for dyskinesia in PD. Additionally, we will gather information on the usability of these assessments for other studies.
Relevance to Diagnosis/Treatment of Parkinson’s Disease:
This study will establish the effects of person-specific placebo-response factors on various rating scales of dyskinesia in patients with PD. This information will allow investigators to know the susceptibility of the different scale to placebo-response effects, and select the most appropriate rating scale for their specific study. The investigators will be in a better position to judge the likelihood and magnitude of a given treatment independent from the effects of placebo-response.
We anticipate two major outcomes with this study. The first will be to assess the impact of person-specific placebo-response factors of dispositional optimism, social conformity, expectations of outcome, and impulsivity on the sensitivity of different dyskinesia rating scales to detect improvement in dyskinesia. The second outcome will be to assess the impact of these person-specific placebo-response factors on the sensitivity of the different ratings scales to distinguish treatment effects from placebo effects.
Professor at Rush University Medical Center
Location: Chicago, Illinois
Associate Professor of Neurology at Duke University Medical Center
Location: Durham, North Carolina, United States