Subcortical tau deposition and plasma glial fibrillary acidic protein as predictors of cognitive decline in mild cognitive impairment and Alzheimer's disease

Purpose This study aimed to investigate the correlation between subcortical tau-positron emission tomography (Tau-PET) and plasma glial fibrillary acidic protein (GFAP) levels and cognitive function in participants with cognitively unimpaired (CU), mild cognitive impairment (MCI) and Alzheimer's disease (AD) conditions. Methods 105 participants with amyloid (A beta) PET and Tau-PET scans were enrolled. Region of interest (ROI) level and voxel-wise comparisons were performed between those three groups. Correlations between standardized uptake value ratio (SUVR) and cognitive performance were analyzed. The diagnostic performance of Tau-PET, A beta-PET, and plasma GFAP, both individually and combined, was evaluated by calculating the area under the curve (AUC) from receiver operating characteristic (ROC) analyses. Results Plasma GFAP levels in the AD and MCI groups were higher than those in the CU group. The AD and MCI groups showed higher Tau-PET load at the amygdala, accumbens, putamen, pallidum, hippocampus, para-hippocampus and olfactory tubercle than the CU group (p < 0.05). In the MCI group, the mean tau SUVR in the combined subcortical ROI negatively correlated with cognitive scores (r = -0.38, p = 0.02). The combination of Tau-PET, A beta-PET and plasma GFAP provided optimal diagnostic accuracy for classifying AD from MCI, with an AUC of 0.82, a sensitivity of 0.69 and a specificity of 0.81. Conclusions Subcortical tau deposition and increased plasma GFAP levels are associated with cognitive impairment in MCI patients.