How the symptoms of Parkinson’s disease progress varies from patient to patient, and it is hard to predict which patients will progress more quickly than others. One way to figure this out is to look carefully at the symptoms of people in early and mild stages of the disease, monitor them closely as their disease progresses, and then see if there are characteristics and symptoms early on that correlate with a better or worse prognosis years later.
We have carefully evaluated about 900 patients seen by a single movement disorders specialist over a 10-year period using the standard and widely used Parkinson’s disease rating scale (Unified Parkinson’s Disease Rating Scale). In addition we have used quantitative measures of how well they were doing including three timed tasks (a timed walk, a block sorting task, and a task involving marking dots in a small grid) as well as a measure of balance called the “Functional Reach.” Balance is not helped significantly by medications, so the Functional Reach measure may be a unique method of assessing disease progression.
Using all of this information, we will analyze which features are most helpful in predicting how fast people with Parkinson’s disease advance in their symptoms.
The researchers found a series of four motor tests to show very good validity, reliability, and efficiency — key elements of a good clinometric scale. The tests showed good correlation with the UPDRS motor score, good test-retest reliability, and a generally high inter-correlation between the tests. All the tests take about the same time as the UPDRS to administer (about five minutes), and less time than many other assessment methods that have been proposed. The associations between the non-traditional measures and the outcomes were generally stronger and more precise than those for the UPDRS motor score. Furthermore, the UPDRS motor score significantly predicted the fewest outcomes and, on a per-standard deviation basis, the UPDRS motor score was a weaker predictor of all outcomes than every non-traditional test, except for the prediction of dementia by functional reach. A global summary score of the four non-traditional motor tests was a particularly good predictor of the outcomes and also correlated extremely well with the UPDRS motor score.
The outcomes predicted by the motor tests include postural instability and falls, depression, dementia, and overall disability.