Estimating premorbid IQ in the prodromal phase of a neurodegenerative disease.

Estimates of premorbid intellect are often used in neuropsychological assessment to make inferences about cognitive decline. To optimize the method of controlling for premorbid intellect in assessments of prodromal neurodegenerative disease, we examined performance on the American National Adult Reading Test (ANART; administered during Years 1 and 3) and the two-subtest version of the Wechsler Abbreviated Scale of Intelligence (WASI; administered in Years 2 and 4) in an ongoing prospective longitudinal study of 371 participants with prodromal Huntington disease and 51 participants with normal CAG repeats. Although both measures performed similarly, the ANART demonstrated slightly lower variability in performance over a 2-year period and had slightly higher test-retest reliability than the WASI.