The Italian Telephone-based Verbal Fluency Battery (t-VFB): Standardization and Preliminary Clinical Usability Evidence

Background: This study aimed at standardizing and providing preliminary evidence on the clinical usability of the Italian telephone-based Verbal Fluency Battery (t-VFB), which includes phonemic (t-PVF), semantic (t-SVF) and alternate (t-AVF) verbal fluency tasks.

Methods: Three-hundred and thirty-five Italian healthy participants (HPs; 140 males; age = 18-96 years; education = 4-23 years) and 27 individuals with neurodegenerative or cerebrovascular diseases were administered the t-VFB. Switch number and cluster size were computed latent semantic analyses. HPs underwent the telephone-based Mental State Examination (MMSE) and Backward Digit Span (BDS). Construct validity, factorial structure, internal consistency, test-retest and inter-rater reliability and equivalence with the in-person Verbal Fluency tasks were assessed. Norms were derived Equivalent Scores. Diagnostic accuracy against clinical populations was assessed.

Results: The majority of t-VFB scores correlated among each other and with the BDS, but not with the MMSE. Switch number correlated with t-PVF, t-SVF, t-AVF scores, whilst cluster size with the t-SVF and t-AVF scores only. The t-VFB was underpinned by a mono-component structure and was internally consistent (Cronbach's α = 0.91). Test-retest (ICC = 0.69-0.95) and inter-rater reliability (ICC = 0.98-1) were optimal. Each t-VFB test was statistically equivalent to its in-person version (equivalence bounds yielding a < 0.05). Education predicted all t-VFB scores, whereas age t-SVF and t-AVF scores and sex only some t-SVF scores. Diagnostic accuracy against clinical samples was optimal (AUC = 0.81-0.86).

Discussion: The t-VFB is a valid, reliable and normed telephone-based assessment tool for language and executive functioning, equivalent to the in-person version; results show promising evidence of its diagnostic accuracy in neurological populations.