Discriminative validity of selected measures for differentiating normal from aphasic performance.

Normal elderly and mildly aphasic individuals may exhibit similar impairments in comprehension and expression. The discriminative validity between normal and aphasic performance on most standardized measures of aphasia has not been reported. The authors compared the performance of 18 aphasic and 18 normal adults to determine the discriminative validity of 2 general language measures--the Porch Index of Communicative Ability (B. E. Porch, 1967) and the Western Aphasia Battery (A. Kertesz, 1982)--and 2 functional communication measures--the Communication Activities of Daily Living-Second Edition (A. L. Holland, C. Frattali, and D. Fromm, 1999) and the American Speech-Language-Hearing Association's Functional Assessment of Communication Skills for Adults (C. Frattali, C. K. Thompson, A. L. Holland, C. B. Wohl, and M. K. Ferketic, 1995). All between-groups comparisons of summary scores for each measure showed significant mean differences. Expressive language ability and efficiency of performance best differentiated between the aphasic and normal groups. However, group performance ranges overlapped by at least 10% on each measure. To enhance the differential diagnosis of aphasia, supplementing formal test results with additional subjective and objective evidence is recommended.