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May 26, 2004

Measuring the Effects of Therapy in Parkinson Disease—Reply

Author Affiliations

Letters Section Editor: Stephen J. Lurie, MD, PhD, Senior Editor.

JAMA. 2004;291(20):2430-2431. doi:10.1001/jama.291.20.2431-a

In Reply: Dr Shults and colleagues discuss unexpected confounding of symptomatic effects of drugs undergoing trial for disease modification, which we also discussed in our article. The study by Shults et al1 was designed as a pilot study based on promising preclinical information and did show a positive trend, particularly in the highest-dose group. However, the study demonstrated changes in activities of daily living scores at 1 month, which had similar P values to the overall study result. This could reflect a symptomatic effect, and it is not possible to know with certainty that this did not influence the primary end point. We applaud the authors for their plans to carry out a fully powered clinical trial. We remain uncertain, however, of which end point will be selected, or how it could be confirmed that positive results represent an effect on disease progression rather than a subtle symptomatic effect.

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