Neuropathologic heterogeneity is often present among
Alzheimer disease (AD) patients. We sought to determine whether
amyloid imaging measures of AD are affected by concurrent pathologies. Thirty-eight clinically and pathologically defined AD and 17 nondemented patients with quantitative
florbetapir F-18 (F-AV-45) positron emission tomography (PET) imaging during life and postmortem histological β-
amyloid quantification and neuropathologic examination were assessed. AD patients were divided on the basis of concurrent pathologies, including those with Lewy bodies (LBs) (n = 21), white matter rarefaction (n = 27), severe
cerebral amyloid angiopathy (n = 11), argyrophilic grains (n = 5), and TAR
DNA binding protein-43 inclusions (n = 18). Many patients exhibited more than 1 type of concurrent pathology. The ratio of cortical to cerebellar
amyloid imaging signal (SUVr) and immunohistochemical β-
amyloid load were analyzed in 6 cortical regions of interest. All AD subgroups had strong and significant correlations between SUVr and histological β-
amyloid measures (p μ 0.001). All AD subgroups had significantly greater
amyloid measures versus nondemented patients, and mean
amyloid measures did not significantly differ between AD subgroups. When comparing AD cases with and without each pathology, AD cases with LBs had significantly lower SUVr measures versus AD cases without LBs (p = 0.002); there were no other paired comparison differences. These findings indicate that
florbetapir-PET imaging is not confounded by neuropathological heterogeneity within AD.