Comparative analysis of qualitative verbal fluency performance in normal elderly and demented populations

Verbal fluency tasks are commonly used in the assessment of patients with known or suspected dementia. Whereas total word production is often analyzed, less attention has been paid to qualitative aspects of verbal fluency performance. The purpose of this study was to examine the diagnostic utility of a qualitative scoring technique for semantic and phonemic fluency tasks in individuals with Alzheimer's disease (AD), Parkinson's disease (PD) with and without dementia, and in a group of older normal controls (ONC). In addition to total words produced, the groups were compared on their use of clustering (i.e., ratio of words generated within subcategories) and switching (i.e., frequency of shifts between clusters) strategies as originally defined by Troyer et al. (1997a). In terms of total number of words produced, controls were superior to the AD and demented PD subjects, who performed similarly. A similar trend was found in relation to switching and clustering scores. PD patients without dementia performed similar to the ONC group on semantic fluency, but were impaired relative to controls on all phonemic fluency variables (i.e., total words produced, clustering, switching). Discriminant function analyses using the three fluency variables revealed that total words was equal to or surpassed the other variables in distinguishing the groups, suggesting that these qualitative verbal fluency features may not provide significant additional information in terms of diagnostic utility.