Reliability of the Washington University road test: A performance-based assessment for drivers with dementia of the Alzheimer type

Objective: To assess the reliability and stability of a standardized road test for healthy aging people and those with dementia of the Alzheimer type (DAT). Design: A prospective study involving patients with DAT and age- matched healthy controls in which subjects' driving performance was evaluated by several raters in an initial and a follow-up road test. Setting: Urban medical school and urban highways and streets. Subjects: A convenience sample of 58 controls, 36 subjects with very mild DAT, and 29 subjects with mild DAT. Results: Analysis of road test ability of controls (2 subjects [3%] failed the test), very mild DAT subjects (7 subjects [ 19%] failed), and mild DAT subjects (12 subjects [41%] failed) disclosed a significant association between driving performance and dementia status (χ²[4]=20.65 [N = 123]; P<.001; Kendall τ-b=0.306). Interrater reliability for assessment of driving performance ranged from κ=0.85 to 0.96. One-month test-retest stability on the road test was 0.76 (quantitative scoring) and 0.53 (clinical judgment). Conclusions: Dementia adversely affects driving performance even in its mild stages, although some persons with DAT seem to drive safely for some time after disease onset. A traffic-interactive, performance-based road test that examines cognitive behaviors provides an accurate and reliable functional assessment of driving ability.