Identifying Safe Drivers With Parkinson’s Disease

Four clinical variables can predict fitness to drive in 90% of patients with Parkinson’s disease, according to a study in the October 2 Neurology. A screening battery that measures disease duration, contrast sensitivity, and cognitive and motor functions predicted fitness to drive in patients with Parkinson’s disease with a high degree of accuracy, reported Hannes Devos, MSc, and colleagues.

In this prospective study of 40 patients with Parkinson’s disease and 40 age- and gender-matched controls, 29 patients (72.5%) were qualified to “drive without restrictions.” Ten patients were judged as “fit to drive with restrictions,” and one patient was classified as “unfit to drive.”

Eight patients (20%) with Parkinson’s disease misjudged their driving abilities. Of these, five patients (12.5%) thought that they should be able to drive without restrictions, but testing suggested that four required restrictions and one should not drive at all. Conversely, three patients (7.5%) thought that they should be able to drive only with restrictions, but testing suggested that they were capable of unrestricted driving.

The authors examined multiple clinical variables to devise a streamlined driving assessment test battery, including age, gender, disease duration, levodopa dosage, Hoehn and Yahr score, driving experience, distance driven annually, traffic penalties, and accidents. Clinical assessments such as the Epworth Sleepiness Scale, Pelli-Robson contrast sensitivity, the Rey-Osterreith Complex Figure Test (copy subtest), the Clinical Dementia Rating (CDR), and the Unified Parkinson’s Disease Rating Scale (UPDRS) parts II and III were also used in the analysis. In addition, all patients participated in a driving simulator evaluation.

To enroll in the study, patients had to be regularly driving without restriction and have a Hoehn and Yahr score of 1 to 3, a CDR of 1 or less, and adequate vision. Patients with deep brain stimulators and unpredictable motor fluctuations were excluded.

Patients with Parkinson’s disease were also evaluated by the Center for Fitness to Drive Evaluation and Car Adaptations (CARA) of the Belgian Road Safety Institute, recognized as the gold standard for comparison. The analysis included a three- to four-hour assessment by a physician, a neuropsychologist, and a driving expert, and it consisted of medical, visual, and cognitive tests, as well as an evaluation on the road. The screening battery that best correlated with the CARA evaluation included the CDR, disease duration, visual contrast sensitivity, and UPDRS motor score. Compared with the CARA assessment, these four objective measures resulted in 90% specificity and 91% sensitivity.

When a more contextual test such as a driving simulator was added to the clinical model, the predictive accuracy increased to 97.5%, with a specificity of 100% and a sensitivity of 91%.

The authors recommended that people with Parkinson’s disease who pass the screening battery be allowed to drive, but those who fail should receive further evaluation at a specialized center with more comprehensive driving tests. Given the progressive nature of Parkinson’s disease, patients should be reevaluated periodically, depending on the rate of disease progression.

Dr. Devos, of the Katholieke Universiteit Leuven in Belgium, explained that the four-part battery is a practical tool for physicians that can be administered in the clinical setting in 30 to 45 minutes.           

NR