Normative Reference Values for Crystallized–Fluid Discrepancy Scores for the NIH Toolbox Cognition Battery

Abstract

Abstract Introduction The purpose of this study was to translate NIH Toolbox Cognition Battery (NIHTB-CB) Crystallized–Fluid discrepancy scores into research and clinical practice with adults by providing normative data for discrepancy scores for both age-adjusted standard scores (SSs) and demographically adjusted T-scores. Method We included adult participants from the NIHTB-CB standardization sample who denied having neurodevelopmental, medical, psychiatric, or neurological conditions (n = 730; M = 47.4 years old, SD = 17.6, range: 18–85; 64.4% women; 63.1% White). Descriptive statistics were calculated for the Fluid and Crystallized composite scores and Crystallized–Fluid discrepancy score, along with correlations between the composite scores and reliability estimates of the discrepancy score. Percentiles were calculated for the discrepancy score, with stratifications by the gender, education, and Crystallized composite for the age-adjusted SSs and demographically adjusted T-scores (T). Results Crystallized–Fluid discrepancy scores ranged from −40 to 44 (M = −0.63, SD = 14.89, Mdn = −1, interquartile range [IQR]: −11 to 10) for age-adjusted SSs and from −29 to 27 (M = −0.39, SD = 10.49, Mdn = −1, IQR = −8 to 7) for demographically adjusted T-scores. Crystallized–Fluid discrepancy scores of SS = 15 and T = 11 were at the 16th percentile (1 SD below the mean) and discrepancy scores of SS = 21 and T = 15 were at the 7th percentile (1.5 SD below the mean). Conclusions Crystallized–Fluid discrepancy scores may be, with future research, a useful within-person interpretive approach for detecting a decline from pre-injury or pre-disease levels of cognitive functioning. These normative reference values assist clinicians and researchers in determining the frequency at which given Crystallized–Fluid discrepancy scores occurred among healthy adults in the normative sample.