Predictors of Driving Assessment Outcome in Parkinson's Disease

This study evaluated selected clinical and functional tests as predictors of driving safety outcomes in Parkinson's Disease (PD) patients. Twenty five PD patients and 21 age-matched controls, all regular drivers, underwent neurological evaluation and assessment of cognitive, visual and motor function and a standardised, on-road driving assessment. The capacity of the tests to predict pass/fail driving outcomes was determined by selecting a sub-set with the highest predictive value from each domain and then subjecting these to discriminant function analysis. Accuracy, sensitivity, specificity and positive and negative predictive values were determined. Three relatively simple tests from the larger battery predicted passes with relatively high sensitivity (PD: 72.7%, controls: 93.8%, both combined: 85.2%); and moderate specificity (PD: 64.3%, controls: 60.0%, both combined: 63.2%). These tests assessed motor performance (Purdue Pegboard test), contrast sensitivity (Pelli-Robson test) and cognitive function (verbal version of Symbol Digit Modalities Test). Adding time since diagnosis for the PD group increased sensitivity to 90.9% and specificity to 71.4 %. These simple tests confer more objectivity and predictive power to clinical recommendations for driving, they reflect distinct functions that are necessary for safe driving, and may be especially useful when on-road assessments are not feasible