Use of the North American Adult Reading Test to Estimate Premorbid Intellectual Function in Patients with Multiple Sclerosis

The North American Adult Reading Test (NART-R) has proven to be a valid means of estimating premorbid intellectual function in a variety of neurologic patient samples. The NART-R was administered to a group of patients with multiple sclerosis (MS) varying in course and degree of physical disability and healthy controls as part of an extensive neuropsychological battery examining numerous verbal cognitive functions, particularly language. The MS sample demonstrated significantly worse NART-R performance than did controls which could not be explained by differences in estimated premorbid intellectual function. Patients with a chronic-progressive course specifically obtained significantly lower scores than did controls, whereas there were no differences in the scores obtained by patients with chronic-progressive and relapsing-remitting courses or by patients with a relapsing-remitting course and controls. Thus, NART-R performance may not be a valid estimate of baseline IQ for patients with neurologic disorders with suspected language impairment.