CORRELATION BETWEEN AMYLOID IMAGING AND CLINICAL DEMENTIA RATING IN AMNESTIC MILD COGNITIVE IMPAIRMENT AND VERY MILD ALZHEIMER’S DISEASE DEMENTIA

Abstract

It is difficult to clearly dichotomize amnestic mild cognitive impairment(aMCI) and very mild Alzheimer's dementia(AD) by clinical diagnosis. We evaluate the difference of amyloid imaging between aMCI and very mild AD belonging to clinical dementia rating(CDR) 0.5. We investigate the correlation in individual CDR domain and regional/total Standard Uptake Value ratio (SUVR) in amyloid positron emission tomography(PET). This study included 42 aMCI and 21 AD patients. PET with Pittsburgh compound B(PIB) measured global cortical amyloid retention to classify a participant as positive or negative for amyloid. Each participant's amyloid burden was quantified through the computation of SUVR in frontal, temporal, parietal, cingulate area, and totally. Basic demographics, percentage of APOE ε4 carrier were similar, but CDR sum of boxes(SOB) scores were different between two (1.5 ± 0.9 vs 3.1 ± 0.8, P<0.001). PIB(+) was different (aMCI 57.1% vs AD 95.2%). All regional and total SUVRs showed significant differences between two. However, after selecting PIB(+) patients (aMCI 24, AD 20), even though CDRSOB scores were statistically different (1.6 ± 0.8 vs 3.0 ± 0.8, P<0.001), there were no statistical differences in all regional and total SUVRs between two. According to APOE genotype, APOE ε4 carriers showed relatively higher frontal, parietal, cingulate, and total SUVRs in aMCI, while there were no differences in AD. In all participants, CDR 1(memory) and 2(orientation) domain showed positive correlation with all regional and total SUVRs, while CDR 3(judgement & problem solving), 4(community affairs), 5(home and hobbies), and 6(personal care) domains had no correlation with SUVRs. In aMCI, CDR 2 domain had positive correlation with almost regional SUVRs except parietal area, while CDR 1,3,4,5,6 had no correlation with SUVRs. In AD, there were no correlation between CDR domains and SUVRs. In only PIB(+) participants, there were no correlation between individual CDR domain and regional/total SUVRs. The prevalence of PIB(+) was different between aMCI and AD, which suggests that aMCI has heterogeneity. APOE genotype influence SUVRs in aMCI, not AD. It suggests that amyloid imaging might be useful to differentiate heterogeneity of MCI, but not valuable to differentiate aMCI and very mild AD in PIB(+) patients.