Multiple category verbal fluency in mild cognitive impairment and correlation with CSF biomarkers for Alzheimer's disease

Background: Verbal fluency (VF) tasks are widely used in neuropsychological evaluations, as a measure of executive/semantic dysfunction. The revised criteria for Alzheimer's disease (AD) diagnosis (National Institute on Aging and the Alzheimer Association, 2011) incorporating biomarkers has increased the interest in finding algorithms that combine neuropsychological and biomarkers features to better predict conversion from mild cognitive impairment (MCI) to AD. Our aim was to compare the most frequently used VF categories to determine which best discriminated cognitively healthy elderly from MCI patients, and whether cerebrospinal fluid (CSF) biomarkers levels (A beta 42, P-tau, T-tau, and A beta 42/P-tau) correlated with patient's performance in MCI. Methods: We studied 37 cognitively healthy elderly and 30 MCI patients in five VF tasks (animal, fruits, means of transportation, FAS-COWA, and verbs); 23 controls and 19 MCI patients had their CSF biomarkers for AD determined. Results: MCI group performed worse than controls in all VF tasks (p < 0.0001). The cut-off scores were: 14 (animals) (AUC = 0.794), 12 (fruits and means of transportation) (AUC = 0.740 and 0.719, respectively), 41 (FAS) (AUC = 0.744), and 11 (verbs) (AUC = 0.700). The model "animal plus FAS-COWA" was the best to discriminate both groups (AUC = 0.833) (all p < 0.05). MCI produced fewer words than controls in the second-half of the task for all categories (p < 0.001). T-tau levels were negatively correlated to animal fluency (r=-0.485, p = 0.035), and showed a trend for negative correlation with fruits fluency (r=-0.4429, p = 0.057). Conclusions: Animal fluency alone and combined to FAS-COWA was slightly superior in discriminating controls from MCI (p < 0.001), and correlated to T-tau levels.