Cerebrospinal fluid tau protein levels and 18F-fluorodeoxyglucose positron emission tomography in the differential diagnosis of Alzheimer's disease.

AIMS In this study, we aimed to compare cerebrospinal fluid (CSF) levels of total tau (t-tau), phosphorylated tau (p-tau(181)) and positron emission tomography with (18)F-fluorodeoxyglucose (FDG-PET) in the differential diagnosis of Alzheimer's disease (AD) under clinical conditions. METHOD In a cross-sectional, blinded, single-center study, we examined a sample of 75 unselected memory clinic patients with clinical diagnoses of dementia of Alzheimer type (DAT; n = 24), amnestic mild cognitive impairment (MCI; n = 16), other dementias (n = 13) and nondemented controls (n = 22). Discriminative accuracy, sensitivity and specificity were calculated and compared using ROC analyses. RESULTS p-tau(181) and FDG-PET were comparable in separating DAT from controls (sensitivity: 67 vs. 79%; specificity: 91% for both) and patients with other dementias (sensitivity: 71 vs. 79%; specificity: 100% for both). The sensitivity of p-tau(181) in differentiating MCI patients from controls was significantly (p < 0.05) superior to that of FDG-PET (75 vs. 44%) at a comparably high specificity (82 vs. 91%); t-tau measures were less accurate in all analyses. CONCLUSIONS FDG-PET and CSF p-tau(181) levels are able to discriminate DAT in heterogeneous and unselected samples with a high accuracy. CSF p-tau(181) might be somewhat superior for a sensitive detection of patients with MCI.