ROC curve analysis revealed that plasma GFAP allowed a reliable differential diagnosis between PDD and PD-NC (AUC = 0.79), PD-MCI (AUC = 0.74) or PD with non-dementia (including both PD-NC and PD-MCI, AUC = 0.77) (Fig. 1d). This evidence concerns the gene GFAP and Parkinson disease.