P4‐104: CLINICAL SIGNIFICANCE OF FOCAL ¹⁸ F‐FLUTEMETAMOL UPTAKE

Presence of ß-amyloid (Aß) in the brain can be detected using amyloid PET. In clinical practice, interpretation of amyloid PET relies on dichotomous visual rating which guides focal Aß uptake to be read as positive for amyloid. However, the characteristics of focal Aß uptake is not well established. Therefore, we aimed to characterize patients with focal Aß uptake in terms of cognition and cerebrospinal fluid (CSF) level of amyloid and tau. We included 129 subjects (68 subjective memory impairment, 38 mild cognitive impairment, and 23 Alzheimer's dementia) from 8 referral centers. All patients underwent neuropsychological tests and 18F-flutemetamol PET. 74 patients underwent CSF analysis. Each 18F-flutemetamol PET scan was visually assessed in 10 regions (frontal, posterior cingulate and precuneus, lateral temporal, parietal, and striatum of each hemisphere) and was classified into three groups: No-Aß, Focal-Aß (amyloid uptake in 1-9 regions) and Diffuse-Aß (uptake in all 10 regions) groups. We compared cognitive function, CSF amyloid, and CSF tau across the three groups. Of the 129 subjects, 80 subjects were classified as No-Aß, 21 subjects as Focal-Aß and 28 subjects as Diffuse-Aß group. Focal-Aß group performed better in memory and global cognitive function tests compared to Diffuse-Aß group, while there was no significant difference compared to No-Aß group. Moreover, Focal-Aß group showed increased levels of CSF Ab42 and decreased levels of CSF t-tau, p-tau, t-tau/Aß42, p-tau/Aß42 compared to Diffuse-Aß group, while there were no differences compared to No-Aß group. Our result revealed that cognition and levels of CSF amyloid and tau in Focal Aß uptake subjects were different from Diffuse Aß uptake subjects. Further studies are needed to elucidate clinical significance of focal Aß uptake in larger longitudinal studies.