O5–02–01: Comparison of Amyloid Profiles Using CSF and Cortical Florbetapir‐pet Imaging in Prodromal Alzheimer's Disease

Florbetapir (AV-45) PET imaging has been shown to be a reliable tool to assess amyloid load in patients with Alzheimer's disease. Cerebrospinal fluid (CSF) sampling has already shown correlations with the presence of amyloid plaques, even at early stages. In this study, we investigated individual cortical AV-45 binding and CSF profiles in highly selected patients at the prodromal stage of Alzheimer's disease. Patients were selected according to recent criteria, using neuropsychological assessment, MRI, FDG, and CSF sampling. Selected patients then underwent AV-45 PET imaging. Matched cognitively normal controls underwent the same investigation except CSF sampling. Individual CSF and AV-45 binding profiles were compared for each patient. To eliminate non-specific AV-45 uptake in white matter from our analyses, we developed a technique to assess cortical AV-45 binding only. Sensitivity and specificity were determined for cortical AV-45 uptake in regions of interest (ROI) using ROC curve analysis. CSF profiles were established using A β 42, A β 40, Tau and phosphorylated-Tau concentrations and ratios. 22 prodromal patients and 17 cognitively normal controls were included in the study. All patents underwent AV-45 PET, and 19 of them had CSF sampling. The precuneus was the ROI that best discriminates the patients from healthy subjects, with a specificity of 100% and a sensitivity of 77% at a cut-off for AV-45 uptake values of 1.32. At this cut-off, 17 patients out of 22 were considered AV-45 positive. Regarding CSF, 18 out of 19 patients had a profile consistent with AD. When comparing the two modalities, five patients had non-congruent amyloid profiles. These results suggest that, if used for clinical diagnosis of AD, physiopathological markers such as AV-45 PET imaging and CSF sampling need to be combined to other markers. They also suggest that CSF may show a best sensitivity at prodromal stage.