Objective: To determine whether clinical certainty ratings are helpful in predicting pathologically proven PD.

Background: Clinical diagnostic criteria for PD rely on rest tremor, bradykinesia, and rigidity. These features are non-specific and neuropathological confirmation remains the gold standard for diagnosis. This study compares clinical certainty ratings in autopsy proven PD.

Methods: Data was obtained from the Arizona Study of Aging and Neurodegenerative Disorders (AZSAND). Subjects were assessed annually by a movement disorders specialist and assigned to one of four clinical certainty groups based on clinical features at the last examination prior to autopsy (0-9%, 10-49% 50-89%, and 90-100% certainty). Certainty was subjectively determined by the examiner and was based on the presence of historical information and clinical findings. As the 0-9% certainty group had only 5 cases they were grouped with the 10-49% group, leaving Group I: 0-49%, Group II, 50-89% and Group III: 90-100%. All subjects were autopsied and had a standardized neuropathological assessment.

Results: 250 subjects were assigned a PD certainty at their last visit. Group I had 71 subjects, Group II 51, and Group III 128. The clinical features documented in Group I v/s II v/s III are as follows: rest tremor (52% v/s 69% v/s 64%), bradykinesia (69% v/s 98% v/s 100%), rigidity (15% v/s 66% v/s 90%), postural instability (50% v/s 68% v/s 94%), asymmetric onset (53% v/s 70% v/s 83%), persistent asymmetry (55% v/s 68% v/s 49%), current response to treatment (0% v/s 16% v/s 94%), motor fluctuations (0% v/s 16% v/s 55%), and dyskinesia (0% v/s 16% v/s 38%). Rigidity, postural instability, asymmetric onset, current response to treatment, motor fluctuation, and dyskinesia were more likely to be present in the group rated with a higher certainty. The final diagnosis of PD was confirmed by neuropathological assessment in 86% of the patients in Group III, 32% in Group II, and 5% in Group I.

Conclusions: Using a predictive certainty scale for the clinical diagnosis of PD may be useful in clinical trials. High certainty (90-100%) had strong positive predictive value (86%) for autopsy proven PD as compared to either lower certainty groups (0-49% and 50-89%) which had lower predictive value (5% and 32% respectively). As higher certainty (Group III) was associated with medication response, using these PD certainty groupings may not be helpful in drug naive subjects.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/are-clinical-certainty-ratings-helpful-in-the-diagnosis-of-parkinsons-disease/