Premorbid estimates of neuropsychological functioning for diverse groups.

One of the basic tasks performed by a neuropsychologist is to identify the difference between current performance and the premorbid expected performance. Baseline expected performance for Intellectually Impaired (n = 21), Developmentally Delayed (n = 40), Attention Deficit Disorder (n = 98), Learning Disability (n = 42), and "Normal" groups (n = 75) were developed along with a demographically corrected prediction of premorbid functioning and a word reading based prediction of premorbid functioning. We utilized a subset of this data pool for development (n = 107) and validation (n = 108) of premorbid functioning estimates. Findings show that a combination of three methods (baseline, demographic, and reading) were superior to any individual method. The effect size (Cohen's d) calculations show that differences in the prediction of domain level performances were small and likely not clinically meaningful, indicating that the premorbid estimates would be usable as a prediction of expected performance at the domain level. However, the motor domains were not well predicted.