Florbetapir-PET to diagnose cerebral amyloid angiopathy

Objective: We hypothesized that florbetapir, a Food and Drug Administration-approved PET tracer, could distinguish cerebral amyloid angiopathy (CAA)-related intracerebral hemorrhage (ICH) from hypertensive ICH (HTN-ICH). Methods: We prospectively enrolled survivors of primary ICH related to probable CAA (per Boston Criteria, n = 10) and HTN-ICH (n = 9) without dementia. All patients underwent florbetapir-PET and multimodal MRI, and patients with CAA had additional Pittsburgh compound B (PiB) PET. Amyloid burden was assessed quantitatively (standard uptake value ratio [SUVR]) and visually classified as positive or negative. Results: The CAA and HTN-ICH groups had similar age (66.9 vs 67.1), sex, and leukoaraiosis volumes (31 vs 30 mL, all p> 0.8). Florbetapir uptake and PiB retention strongly correlated in patients with CAA both globally within cerebral cortex (r= 0.96, p< 0.001) and regionally in lobar cortices (all r> 0.8, all p[< or =] 0.01). Mean global cortical florbetapir uptake was substantially higher in CAA than HTN-ICH (SUVR: 1.41 + or - 0.17 vs 1.15 + or - 0.08, p= 0.001), as was mean occipital SUVR (1.44 + or - 0.12 vs 1.17 + or - 0.08, p< 0.001), even after correcting for global SUVR (p= 0.03). Visual rating for positive/negative florbetapir demonstrated perfect interrater agreement (k = 1) and was positive for all 10 patients with CAA vs 1 of 9 HTN-ICH patients (sensitivity 100%, specificity 89%). Conclusions: Florbetapir appears to label vascular amyloid in patients with CAA-related ICH. The approved florbetapir binary visual reading method can have diagnostic value in appropriate clinical settings.