Purpose/Objective
To apply multivariate base rate analyses to the National Institutes of Health Toolbox Cognition Battery (NIHTB-CB) to facilitate the identification of cognitive impairment in individuals with traumatic brain injury (TBI).
Research Method/Design
In a multisite cross-sectional design, 158 participants who sustained a complicated mild or moderate TBI (n=74) or severe TBI (n=84) at least one year earlier were administered the NIHTB-CB. The NIHTB-CB is comprised of two crystallized cognition tests (reflecting premorbid ability) and five fluid cognition tests, measuring processing speed, memory, and executive functioning. Base rates for obtaining 0 to 5 low fluid cognition scores were calculated across a range of cutoffs for defining a low test score (≤25th to 5th percentiles). Base rates of low scores in the TBI sample were compared to the NIHTB-CB normative sample using diagnostic accuracy statistics.
Results
The proportion of the TBI sample obtaining low scores decreased as the cutoff for defining a low score decreased. Individuals with lower premorbid cognitive ability, as measured by NIHTB-CB crystallized composite score, tended to produce more low scores on the NIHTB-CB fluid cognition tests, even when using fully demographically-adjusted scores. Certain patterns of low scores were associated with TBI (defined as Likelihood Ratio>2.0), whereas others were non-specific, occurring almost as often in participants without TBI.
Conclusions/Implications
Premorbid ability stratified base rate tables provided in this article can guide researchers and clinicians in the interpretation of NIHTB-CB performance in adults with TBI.