Stats Forum


This forum is moderated by the PPMI Statistics Core, led by Christopher Coffey, PhD, co-director of the Clinical Trials Statistical and Data Management Center at the University of Iowa.

The purpose of this forum is to help investigators who are interested in accessing or who have accessed the PPMI database find additional information about the dataset.    *Watch this brief, helpful overview of how to access and use the PPMI data from the Statistics Core.*

 The Statistics Core will respond to questions individually and determine whether the Q & A should be posted publicly on this page or in the Data FAQ. Questions that are posted publicly will not display identifying information about the investigator.


Data and Statisticians Forum

What planned analyses are included in the PPMI protocol?
There are currently a number of analyses planned as part of the initial PPMI protocol. First, there will be a formal comparison of baseline characteristics among healthy controls and PD subjects. There will also be a comparison of short-term change in a number of variables identified as possible progression endpoints. Finally, a formal evaluation will be performed to determine whether short-term changes in progression endpoints are predictive of change in long-term endpoints. The goal of this analysis is to attempt to provide a subset of short-term progression endpoints and suggest biomarkers for future studies of interventions in PD patient populations.

A similar analysis will be performed to compare PD subsets in an attempt to determine whether some short-term progression endpoints are more predictive of long-term endpoints for some subsets of PD patients and less predictive for other subsets.

In 2011, a SWEDD (Scan Without Evidence of Dopaminergic Deficit) cohort was added to the PPMI study.  Correspondingly, additional planned analyses were included.  First, the study will examine the proportion of SWEDD subjects that have a change in their diagnosis over a 24 month evaluation period.  We will also assess any important differences observed among the PD subjects and healthy controls in this SWEDD cohort. These analyses will help to clarify whether changes over time in SWEDD subjects are similar or dissimilar to changes over time in PD subjects.


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