Interpreting High Scores on the NIH Toolbox Cognition Battery: Potential Utility for Detecting Cognitive Decline in High-Functioning Individuals

Objective: It is well established that it is common for healthy adults to obtain one or more low scores when multiple neuropsychological tests are administered; however, very little is known about the normal frequency of high scores. The current study reports high-score base rates for the National Institutes of Health Toolbox for the Assessment of Neurological and Behavioral Function Cognition Battery (NIHTBCB) normative sample. We hypothesized that high scores would be common and increase in frequency with greater education and crystallized ability. Method: Participants (ages 20-85) completed the NIHTB-CB (2 crystallized tests and 5 fluid tests). Multivariate base rates of high age-corrected and demographic-corrected scores for the fluid tests (i.e., ≥50th, 63rd, 75th, 84th, 91st, 95th, 98th percentiles) were calculated with stratifications by education and crystallized ability. Results: High scores occurred commonly on the NIHTB-CB, with 48.9% of participants obtaining 1 + age-corrected scores at or above the 84th percentile. High scores increased in frequency with greater education: 27.5% with 12 years of education had 1 + scores at or above the 91st percentile, whereas 40.7% with 16 or more years of education had 1 + scores at or above the 91st percentile. High scores also increased in frequency with higher crystallized ability: 51.4% of participants with low ability had 1 + demographic-corrected scores at or above the 75th percentile, whereas 81.8% of participants with superior ability had 1 + demographiccorrected scores at or above the 75th percentile. Conclusion: High scores occurred commonly among the NIHTB-CB normative sample and increased in frequency with greater education and crystallized ability. These base rates could inform the neuropsychological assessment of high-functioning individuals, in whom the absence of high scores, as opposed to the presence of low scores, may indicate a decline in cognitive functioning.