Cognitive deficits and clinical diagnosis of Alzheimer's disease.

We used cognitive deficits detected by neuropsychological testing to evaluate clinical diagnosis of Alzheimer's disease. Deficits were defined with respect to performance of control subjects according to procedural guidelines set by a NINCDS-ADRDA Work Group. The most frequent deficits were in recent memory and lexical-semantic language abilities. Clinical diagnosis of Alzheimer's disease was compared with diagnosis based on a criterion of two or more cognitive deficits both on initial neuropsychological testing and on testing repeated a year later in some subjects. Initial clinical diagnosis identified 96% of cases who met the criterion when first tested and 100% of those with multiple deficits at follow-up. Specificity with respect to the criterion was 86% on initial testing and 89% at follow-up. These findings support the validity of clinical diagnosis of Alzheimer's disease using the NINCDS-ADRDA criteria.