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 (chi 2[4] = 20.65 [N = 123]; P < .001; Kendall tau-b = 0.306). Interrater reliability for assessment of driving performance ranged from kappa = 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.