New PPMI Cohort Designation Methodology

Accessing and Understanding Data
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Hello, everyone. I just wanted to highlight something that changed recently due to a methodological modification regarding cohort designation in PPMI. This modification took place on August 28, 2024, so it may still be relatively new to most of us.

Prior to this modification, PPMI provided a specific document designating patients within their cohorts (such as PD, Healthy Controls, etc.). This document was intended to be used separately to identify patients in their respective cohorts and was updated by a committee from the study group. However, following this recent review, we now need to identify patients using the “Participant Status” dataset, which is located under the “Subject Characteristics” heading in LONI.

Additonally, PPMI is now introducing the “Neuronal Synuclein Disease (NSD) Categorization”. As explained in the most recent Data User Guide:

The overall NSD category is based on both the presence of pathologic neuronal α-synuclein (S) and dopaminergic neuronal dysfunction (D).

Here is an image extracted from the most recent Data User Guide explaining this new and optional classification:

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@jgottesman @gginnan, due to this change, we should review the instructions written in our Getting Started With Parkinson’s Disease Data. I can make these changes to the PPMI part, just tell me which document I should edit and the other necessary steps to update the document.

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@danieltds , thank you very much for posting this. As you say, there was a new release of the PPMI data user guide at the end of August. The most significant changes were updates to reflect the end of the Consensus Committee which used to convene to assign participants to categories in the consensus committee analytic dataset; and the introduction of the NSD and NSD-ISS categorizations.

This August release of the PPMI data user guide also contained a few minor updates:

  • Section 5: More explanation of EVENT_ID
  • Section 6.1: Some clarifications around the capture of MDS-UPDRS values
  • Section 6.2: Some clarifications on the handling of missing values in UPSIT data
  • Section 7.1: More detail on calculation of LEDD values
  • Section 15: Verily data is now only available on request
  • Appendix E: contains further details on the derivation of NSD-ISS

The PPMI data model is quite dynamic and in the future there may be further changes to existing datasets and the introduction of new datasets. Going forward, we’ll endeavour to post release notes on this forum when there are updates to the PPMI data user guide.

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