FDG-PET improves diagnosis in patients presenting with focal onset dementias

Alzheimer’s disease is the cause of up to one third of cases of primary progressive aphasia or corticobasal syndrome. The objective of this study was to determine the accuracy of FDG-PET metabolic imaging for detection of Alzheimer’s disease in patients with primary progressive aphasia or corticobasal syndrome. Methods: A cohort of subjects (n = 94) including those with expert clinical diagnosis of logopenic (n = 19), non-fluent (n = 16) or semantic (n = 13) variants of primary progressive aphasia, corticobasal syndrome (n = 14), or Alzheimer’s disease (n = 24) underwent F18-FDG metabolic and C11-PiB amyloid PET brain imaging. FDG-PET scans read with Neurostat 3D-SSP software displays were classified as Alzheimer’s disease or other by readers blind to the clinical assessments and PiB-PET results. PiB-PET imaging was considered the diagnostic reference standard with a threshold standardized uptake value ratio of 1.5 indicative of Alzheimer’s disease pathology. To address biases from subgroup selection for the Alzheimer’s disease binary classifier, both conventional and balanced accuracy were calculated. Results: Diagnoses of Alzheimer’s disease based on FDG-PET resulted in 84% accuracy both conventional and balanced. In comparison, diagnoses based on clinical assessment resulted in 65% conventional and 67% balanced accuracy. Conclusions: Brain FDG-PET scans read with Neurostat 3D-SSP displays accurately detect Alzheimer’s disease in patients presenting with primary progressive aphasia or corticobasal syndrome as focal onset dementias. In these diagnostically challenging cohorts, FDG-PET imaging can provide more accurate diagnoses enabling more appropriate therapy.