Assessments Shape Patients' Perception of Treatment in Parkinson's: Presented
at ANA
By Jacquelyn Beals
WASHINGTON, DC -- October 12, 2007 -- A new study has identified the factors
that shape patients' perception of their treatment received for Parkinson's
disease, researchers noted here in a poster paper at the Annual Meeting of
the American Neurological Association (ANA).
An earlier study comparing the effects of sham surgery with the effects of
actually implanting embryonic dopamine neurons demonstrated that
the "perceived treatment" groups corresponded better with between-group
differences than did the presence or absence of surgical treatment.
Lead author Cynthia A. McRae, PhD, Professor, Counseling Psychology, College
of Education, University of Denver, Denver, Colorado, noted that, "Because
the placebo effect was so strong in this study, it was important to
investigate the predictors of this effect."
Forty patients randomly assigned to surgical or sham surgery groups were
followed for 12 months. The patients' mean age at time of surgery was 57.8
years; mean duration of Parkinson's disease was 15.7 years. Of these
patients, 30 participated in the quality of life (QoL) study, and 22
caregivers responded to a questionnaire.
The information analysed by Dr. McCrae's group included both neurological
assessment and QoL data obtained from patients and partners at 7 days, and 4,
8, and 12 months after surgery (or sham surgery). The study used the Unified
Parkinson's Disease Rating Scale (UPDRS) and assessments of physical,
emotional, and social functioning related to QoL.
Among patients who received embryonic dopamine neurons, and were assessed 7
days post-surgery, 15 subjects believed they had received neurons and five
subjects believed they were sham-operated. By the 12-month evaluation, seven
subjects believed they had received neurons and 12 subjects believed they
were sham-operated.
Among sham-operated patients, assessed after 7 days, 13 subjects believed
they had received embryonic neurons and 6 subjects believed they were
sham-operated. At 12-month evaluations, seven subjects believed they had
received neurons and 13 believed they were sham-operated. As the initial
study concluded, "There was no relationship between the type of surgery
patients actually received and what they thought they received at any time
period after surgery."
The present study found that 12-month results from the UPDRS subscales ("off"
medications) were 74% correct in predicting perceived (not actual) treatment
received (P <.01). Patients' ratings of motor "off" medication scores were
68% correct, and spouses'/partners' ratings were 64% correct in
predicting "perceived treatment" groups (P <.05). Results of the Global
Rating Scale (P <.001) and measures of depression and self efficacy (P <.01)
also reached significant levels in correctly predicting "perceived treatment"
groups.
The authors conclude that the Global Rating Scale is the best predictor of
perceived treatment at 12 months. Measurements of physical functioning by
medical personnel, spouses/partners, and patients also predict perceived
treatment.
It is essential to understand the factors that contribute to the patients'
perception of treatment received, the authors concluded, as it is such a
strong factor in between-group differences.
[Presentation title: Predictors of the Placebo Effect at 12 Months in a
Double-Blind Sham Surgery Controlled Trial. Abstract M-92]
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