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Background. In Parkinson’s disease (PD), verb-naming tasks have been proposed as superior to noun-naming ones in detecting language deficits, although such an hypothesis is not supported at a statistical level. Objectives. Providing diagnostic accuracy evidence for a verb- and noun-naming task in detecting cognitive impairment in PD patients. Method. Thirty-three consecutive PD patients were subdivided into participants with (PD-CI; N=12) or without cognitive impairment (CI) (cognitively unimpaired, PD-CU; N=21), based on a raw score ≤25 or >25 on the Mini-Mental State Examination (MMSE), respectively. The Noun- and Verb-Naming Task (NNT, VNT) by Crepaldi et al. (2006) was administered. Diagnostic accuracy on the NNT and VNT was assessed through receiver-operating characteristics (ROC) analyses by comparing PD-CU to PD-CI patients. At the optimal cut-off, sensitivity, specificity, positive and negative predictive values (PPV, NPV) and likelihood ratios (LR+, LR-) were separately tested for the NNT and VNT against PD-CU vs. PD-CI classification. Results. Diagnostic accuracy was higher for the NNT (AUC =.85; p=.001) vs. the VNT (AUC =.68; p=.092). Consistently, the NNT yielded higher sensitivity, specificity and post-test features than the VNT (NNT: sensitivity =.75; specificity=.81; PPV =.69; NPV =.85; LR+ =3.94; LR- =.31; VNT: sensitivity=.67; specificity =.67; PPV =.53; NPV =.78; LR+ =2; LR- =.5). Conclusions. In accordance with the Movement Disorders Society guidelines, noun-naming tasks are diagnostically sound psychometric instruments to discriminate PD patients with vs. without CI. However, these findings need replication by (1) employing a gold standard different from the MMSE, which does not capture the full range of cognitive impairment in this population and (2) sub-dividing PD patients into those with mild cognitive impairment and dementia.

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