Abstract WMP90: Florbetapir PET to Diagnose Cerebral Amyloid Angiopathy

Abstract

Introduction: Previous studies showed that Pittsburgh Compound B (PiB) labels vascular amyloid characteristic of cerebral amyloid angiopathy (CAA) on PET scans; PiB is not approved for clinical use, however. Hypothesis: We hypothesized that Florbetapir, an FDA-approved PET tracer, can detect amyloid in CAA and help distinguish CAA-related intracerebral hemorrhage (ICH) from hypertensive ICH (HTN-ICH). Methods: We prospectively enrolled non-demented survivors of primary ICH related to probable CAA (per Boston Criteria, n=10) and HTN-ICH (n=9). All patients underwent Florbetapir-PET, multimodal MRI, and additional PiB-PET for the CAA patients. Amyloid burden was assessed quantitatively using parametric maps and also visually, classified as positive or negative. Spatial correlations between Florbetapir and PiB retention were used to test vascular amyloid binding in CAA. We have tested the diagnostic value of Florbetapir by comparing global and occipital mean Florbetapir retention (standard uptake value ratio, SUVR) as well as Florbetapir positive/negative status between CAA and HTN-ICH groups. Results: The CAA and HTN-ICH groups had similar age (66.9 vs 67.1), sex and white matter hyperintensity volumes (31ml vs 30ml, all p>0.8). Florbetapir uptake and PiB retention strongly correlated in CAA patients both globally within cerebral cortex (r=0.96, p<0.001) and regionally in occipital, frontal, temporal, parietal cortices (all r>0.8, all p < 0.01). Mean global cortical Florbetapir uptake was significantly higher in CAA than HTN-ICH (SUVR: 1.41±0.16 vs 1.16±0.08, p=0.001) as was mean occipital SUVR (1.44±0.12 vs 1.17±0.08, p<0.001), remaining independent after correcting for global SUVR (p=0.02). Visual rating for Florbetapir positive/negative demonstrated perfect interrater agreement (k=1) between two trained neurologists blinded to all other information and was positive for all 10 CAA patients vs 1 of 9 HTN-ICH patients (sensitivity 100%, specificity 89%). Conclusions: Florbetapir, like PiB, appears to label vascular amyloid in patients with CAA-related ICH. Data using the approved Florbetapir binary visual reading method suggest sufficient sensitivity and specificity for diagnostic use in appropriate clinical settings.