Objective: An objective of the Parkinson Associated Risk Syndrome (PARS) study is to identify a cohort ‘at risk’ for Parkinson’s disease (PD) using sequential olfactory testing and DAT imaging and evaluate changes in clinical features and imaging markers during the prodromal stage of PD. We report the longitudinal imaging and phenoconversion data of hyposmic individuals without motor signs sufficient for a diagnosis of PD at baseline.

Background: The prodromal phase of PD, estimated to be up to approximately 10 years in duration. The PARS cohort includes 203 hyposmic and 100 normosmic subjects. Data from baseline imaging indicates 11% of subjects have a DAT deficit (<65% of age expected uptake) and appear to be at increased risk for developing PD. We report longitudinal imaging and phenoconversion data at 4-6 years follow-up of hyposmic individuals without a diagnosis of PD at baseline.

Methods: Subjects are evaluated at baseline, 2-, 4- and 6-yrs with clinical and 123I-ß-CIT/SPECT. Clinical evaluations (UPDRS, cognitive testing, diagnosis assignment) and were performed blind to imaging and olfactory data. For this study DAT deficit was defined as <65% of age expected uptake, indeterminate status 65-80% of age expected uptake and no DAT deficit as >80% of age expected uptake. Phenoconversion was defined by clinical investigators blind to imaging and olfactory status.

Results: 203 hyposmics and 100 normosmics completed baseline assessments, 262 completed 2-yr, 173 completed 4-yr visits. Baseline DAT status for hyposimics: 23 (11%) DAT deficit, 41 (20%) indeterminate, 139 (68%) no DAT deficit. Follow-up imaging in subjects with indeterminate DAT status at baseline demonstrates 10/41 (24%) convert to DAT deficit by 4 yrs. Follow-up imaging in subjects with no DAT deficit at baseline demonstrates 7/139 (5%) convert to DAT deficit by 4 yrs. Phenoconversion to PD was identified within 4-yr follow-up for hyposmics with DAT deficit at baseline in 61% (14/23) and for those with DAT deficit at any scan 21/41 (51%).

Conclusions: Longitudinal follow-up of the PARS cohort demonstrates that hyposmics with baseline DAT deficit have a high rate of phenoconversion (61%) within the 4-year follow-up period. Evaluation of subjects that develop DAT deficit during the course of the study period offers the opportunity to prospectively evaluate the duration, changes in clinical features and disease markers during the prodromal period.

« Back to 2016 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/evaluating-the-natural-history-of-prodromal-pd-in-the-pars-cohort/