Florbetapir F18 PET Amyloid Neuroimaging and Baseline Characteristics in Patients with Alzheimer’s Dementia (P3.209)

OBJECTIVE: We compared mild and moderate Alzheimer’s disease (AD) patients with and without evidence of amyloid plaques-- as defined by florbetapir PET (FBP-PET) scan results-- to identify differences in baseline characteristics. BACKGROUND: Clinical diagnosis of AD is challenging (reported sensitivity: 70.9%-87.3%; specificity 44.3%-70.8%). DESIGN/METHODS: Included were patients 蠅55 years old with clinically diagnosed mild or moderate Alzheimer’s dementia who had florbetapir F18 PET (FBP-PET) data (n=390) from two identical solanezumab treatment trials. Baseline characteristics and cognitive and functional measures were compared between FBP-PET positive and negative groups (defined by cutoff standardized uptake value ratio [SUVR]=1.1). RESULTS: There were 87 (22.4%) FBP-PET negative patients. Baseline age, education, and race were similar between groups. Less impairment in FBP-PET negative patients than in FBP-PET positive patients was indicated by mean ADAS-Cog14 (28.2±12.1 vs. 35.2±10.7; p<.0001) and MMSE scores (22.2±3.1 vs. 20.5±3.0; p<.0001). A smaller proportion of FBP-PET negative patients carried the Apo-e4 allele (22.6% vs. 62.8%; p<.0001); homozygotes for the Apo-e4 allele were highly likely to be FBP-PET positive (97.92%). When comparing mild and moderate groups, mild FBP-PET positive patients had lower baseline MMSE scores than negative patients (p=.0005). Moderate FBP-PET positive and negative patients showed no difference (p=.7521). No baseline differences were observed between FBP-PET positive and negative patients or mild/moderate subgroups, on ADCS-ADL, CDR, NPI, or GDS. CONCLUSIONS: 22.4% of patients had negative FBP-PET results, inconsistent with an AD diagnosis despite meeting clinical AD criteria and demonstrating cognitive and functional impairment. No baseline variable reliably differentiated mild or moderate patients without amyloid deposition, though presence of the e4/e4 genotype was highly predictive of amyloid deposition. With only 12.9% of a clinically diagnosed AD population homozygous for the Apo-e4 allele, it is not a reliable biomarker for diagnostic use. Amyloid neuroimaging remains a viable resource to help with the diagnosis of AD. Study Supported by: Eli Lilly and Company Disclosure: Dr. Degenhardt has received personal compensation for activities with Eli Lilly & Company as an employee. Dr. Witte has received personal compensation for activities with Eli Lilly & Co. Dr. Case has received personal compensation for activities with Eli Lilly & Company as an employee. Dr. Yu has received personal compensation for activities with Eli Lilly and Company as an employee. Dr. Henley has received personal compensation for activities with Eli Lilly & Co. as an employee. Dr. Henley holds stock and/or stock options in Eli Lilly & Co. Dr. Hochstetler has received personal compensation for activities with Eli Lilly & Co. as an employee. Dr. DSouza has received personal compensation for activities with Inventiv Clinical, LLC. as an employee. Dr. Trzepacz has received personal compensation for activities with Eli Lilly & Co. as an employee.