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Serial Trichotomization to Determine Fitness to Drive: Results From a Cohort of Clients Referred to a Neurology
Michel Bédard1, Hillary Maxwell2, Sacha Dubois3
1Michel Bédard, PhD, is Director, Center for Research on Safe Driving, and Professor, Department of Health Sciences, Lakehead University, Thunder Bay, Ontario, Canada, and Scientific Director, Center for Applied Health Research, St. Joseph's Care Group, Thunder Bay, Ontario, Canada; mbedard@lakeheadu.ca.
Importance:
Determining cognitive fitness to drive is challenging. A previous study used serial trichotomization with five cognitive tests to determine whether drivers should continue driving, undergo further evaluation, or stop driving.
Objective:
To examine agreement between serial trichotomization and fitness-to-drive determinations made by occupational therapists.
Design:
Drivers referred for cognitive screens completed all tests used in the previous study. Occupational therapists provided fitness-to-drive recommendations (safe, indeterminate, or unsafe) using all clinical information available. We examined the agreement between the tests' results (using cut points from the previous study) and occupational therapists' recommendations.
Setting:
Outpatient neurology program at a chronic care and rehabilitation hospital.
Participants:
279 clients (M age = 66.35 yr; SD = 13.25).
Outcomes And Measures:
Tests included the Trail Making Tests A and B, the Clock Drawing Test (CDT), the Montreal Cognitive Assessment, and the Motor-Free Visual Perception Test, using a road test as the gold standard. The previous study used dual cut points with 100% sensitivity and specificity to reduce false positives and false negatives.
Results:
Weighted κs ranged from .03 (95% confidence interval [CI] [-.01, .08]) for the CDT to .54 (95% CI [.46, .62]) for the Trail Making Test, Part B. Although the agreement between serial trichotomization and the final recommendations was moderate (κ = .59; 95% CI [.50, .67]), serial trichotomization appeared useful for identifying unsafe drivers.
Conclusions And Relevance:
These results remind us of the variability inherent in stand-alone cognitive tests, even within a serial trichotomization framework, and the importance of clinical judgement and road tests in decision making about driving. Plain-Language Summary: It can be challenging for occupational therapists to accurately determine a client's cognitive fitness to drive. Many occupational therapists lack the time, have limited training, or do not have access to comprehensive driving evaluation tools. A serial testing approach can support occupational therapists in assessing a client's cognitive fitness to drive. This study used an approach based on a series of five cognitive tests to determine whether a client should continue driving, undergo further evaluation, or stop driving. The series of tests were used to classify drivers as safe, indeterminate, or unsafe. In principle, a driver would take the second test only if the driver was classified as indeterminate on the basis of first test, and so on. By applying the tests in sequence, few drivers should remain classified as indeterminate at the end of the series of tests. This serial approach has the potential to streamline the decision-making process for occupational therapists by classifying the more extreme unsafe cases while still providing an accurate assessment of cognitive fitness to drive.
