title: The verbal fluency index: Dutch normative data for cognitive testing in ALS.
abstract: OBJECTIVE
  Executive dysfunction occurs in 30-50% of amyotrophic lateral sclerosis (ALS) patients and is most frequently assessed with the verbal fluency test. The verbal fluency index (VFI) has been developed to correct for slowness of speech in ALS, and reflects the average thinking time per word. However, its use as a marker of cognitive impairment is hindered by the absence of valid norm scores. Therefore, we provide normative data for the VFI.
  
  
  METHODS
  Dutch volunteers were demographically matched to the Dutch ALS population and completed the verbal fluency index (one-minute and three-minute spoken letter fluency). Multiple stepwise linear regression was performed to assess the influence of demographic variables, past medical history and medication use.
  
  
  RESULTS
  273 volunteers participated in this study. Educational level was negatively correlated to one-minute and three-minute VFI performance (r = -0.3 and r = -0.4, p < 0.001, respectively). No correlations for age, gender, medication and past medical history were found. A formula for standardized z-scores, corrected for educational level, for the one-minute and three-minute VFI was calculated.
  
  
  CONCLUSIONS
  We provide Dutch normative data for the spoken verbal fluency index, which can be used internationally, but validation in other languages is recommended. The findings illustrate the importance of valid disease-specific norm scores for time-dependent cognitive tests in ALS.
authors.affiliation: Department of Neurology, Academic Medical Centre, University of Amsterdam , Amsterdam , the Netherlands.
authors.forename: Emma
authors.initials: E
authors.lastname: Beeldman
authors.forename: Bregje
authors.initials: B
authors.lastname: Jaeger
authors.forename: Joost
authors.initials: J
authors.lastname: Raaphorst
authors.forename: Meinie
authors.initials: M
authors.lastname: Seelen
authors.forename: Jan
authors.initials: J
authors.lastname: Veldink
authors.forename: Leonard
authors.initials: L
authors.lastname: van den Berg
authors.forename: Marianne
authors.initials: M
authors.lastname: de Visser
authors.forename: Ben
authors.initials: B
authors.lastname: Schmand
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000690:Amyotrophic Lateral Sclerosis / Q000150:complications*; D016022:Case-Control Studies; D003072:Cognition Disorders / Q000175:diagnosis* / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D009483:Neuropsychological Tests; D012016:Reference Values; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric; D014705:Verbal Behavior / Q000502:physiology*
keywords: Fluency; normative data; verbal fluency index (VFI)