[P3–338]: IN VIVO TAU PET IMAGING IN EARLY‐ONSET ALZHEIMER's DISEASE AND LATE‐ONSET ALZHEIMER's DISEASE

and late stage aMCI showed higher rate of conversion to dementia. In this study, we investigated the tau uptakes, measured by THK 5351 PET, in early stage and late stage aMCI. We hypothesized that late stage aMCI might have more tau burdens than early stage aMCI. Methods: We prospectively recruited 34 normal controls, eight early stage aMCI, and 48 late stage aMCI from Asan and Samsung medical centers. The presence of amyloid-ß was assessed by F-florbetaben PET. Using cerebellar gray matter as a reference region, we measured mean THK 5351 SUVR in the regions that approximates the anatomical definitions of the Braak stages. Results: Frequency of amyloid positivity was 1/34 (3%), 3/8 (37.5%), and 28/48 (58.3%) in NC, early stage aMCI, and late stage aMCI, respectively. Multiple linear regression showed that compared to NC, late stage aMCI, but not early stage aMCI had more THK5351 uptakes in Braak I&II, III&IVand V&VI ROIs. However, after adding amyloid positivity to a previous model, the statistical significance disappeared. Conclusions: Our findings suggested that late stage aMCI showed increased THK5351 uptakes in entire cortex compared to NC, which might be driven by amyloid positivity.