Verbal fluency tests assess global cognitive status but have limited diagnostic differentiation: evidence from a large-scale examination of six neurodegenerative diseases

Abstract

Verbal fluency is widely used as a clinical test but its utility in differentiating between neurodegenerative dementias and progressive aphasias, and from healthy controls, remains unclear. We assessed whether various measures of fluency performance could differentiate between Alzheimer’s disease, behavioural variant of frontotemporal dementia, non-fluent and semantic variants of primary progressive aphasia, progressive supranuclear palsy, corticobasal syndrome, and healthy controls. Category and letter fluency tasks were administered to 33 controls and 139 patients at their baseline clinical visit. We assessed group differences for total number of words produced, psycholinguistic word properties, and associations between production order and exemplar psycholinguistic properties. Receiver Operating Characteristic curves determined which measure could best discriminate patient groups and controls. Total word count distinguished controls from all patient groups, but neither this measure nor the word properties differentiated the patient groups. Receiver Operating Characteristic curves revealed that, when comparing controls to patients, the strongest discriminators were total word count followed by word frequency. Word frequency was the strongest discriminator for semantic variant of primary progressive aphasia versus other groups. Fluency word counts were associated with global severity as measured by Addenbrooke’s Cognitive Examination-Revised. Verbal fluency is an efficient test for assessing global brain-cognitive health but has limited utility in differentiating between cognitively- and anatomically-disparate patient groups. This outcome is consistent with the fact that verbal fluency requires many different aspects of higher cognition and language.

Multivariate word properties in fluency tasks reveal markers of Alzheimer's dementia

“…51 Our results bear clinical implications. Verbal fluency tasks are widely used to assess AD, other neurodegenerative disorders, 1,3,8,10,12,13,16,60 and relevant phenomena, such as cognitive reserve. 70 Yet, standard scoring diminishes their potential for revealing disease-differential markers.…”

Bridging the Gap: Association between Objective and Subjective Outcomes of Communication Performance in People with Parkinson's Disease Evaluated for Deep Brain Stimulation

“…Verbal fluency is supported by a range of cognitive domains, including executive function and language. 12 Phonemic and semantic fluency are supported by different neural networks. That is, phonemic fluency relies on subcortical frontostriatal structures, whereas semantic fluency relies on cortical temporal networks.…”

“…Verbal fluency is supported by a range of cognitive domains, including executive function and language 12 . Phonemic and semantic fluency are supported by different neural networks.…”

“…Verbal fluency tasks rely on multiple cognitive domains including, executive function and language, and are frequently referenced as a cognitive outcome of DBS. 11,12 Confrontation naming tasks, on the other hand, are considered a more direct measure of language ability. 13,14 However, to what extent verbal fluency and naming tasks are related to a patient's perceived ability to communicate before DBS is not established.…”

“…Language‐based tasks, such as verbal fluency and naming tasks, are commonly used in this setting and interpreted taking into consideration demographic variables, including level of education. Verbal fluency tasks rely on multiple cognitive domains including, executive function and language, and are frequently referenced as a cognitive outcome of DBS 11,12 . Confrontation naming tasks, on the other hand, are considered a more direct measure of language ability 13,14 .…”