PHILADELPHIA—Florbetaben imaging can exclude amyloid pathology reliably, according to research reported at the 66th Annual Meeting of the American Academy of Neurology. The imaging technique has a negative predictive value of 96% and can aid the differential diagnosis of dementia by excluding Alzheimer’s disease.
“A negative scan should encourage the physician to search for other causes of cognitive decline and tailor available treatment options,” said Marwan Sabbagh, MD, Research Professor of Neurology at the University of Arizona College of Medicine in Phoenix.
Dr. Sabbagh and his colleagues recruited 74 individuals who were near death for a histopathologic study. Participants underwent florbetaben PET scans and, after their deaths, brain autopsy and final neuropathologic diagnosis. The radiologists and pathologists were blinded to the patients’ treatment diagnoses.
Of the 74 individuals, 57 had Alzheimer’s disease, and 44 of these latter participants were amyloid positive. Three patients had been diagnosed with Lewy body dementia, six patients had been diagnosed with other dementia, and eight patients were nondemented. A total of 47 patients in the sample were amyloid positive.
Florbetaben imaging had a sensitivity of 98% for detecting amyloid pathology. The technique correctly identified 46 of 47 participants as amyloid positive. Florbetaben imaging had a specificity of 89%. The presence of other neuropathology did not influence the assessment of the scans.
A positive amyloid scan had a standardized uptake value of 1.71, and a negative amyloid scan had a standardized uptake value of 1.24. Receiver operating characteristic analysis suggested that 1.478 is the optimal cutoff for sensitivity and specificity. This cutoff is “a little bit higher than you see with other radiocontrast agents of amyloid imaging,” Dr. Sabbagh noted.
The research represents the largest sample worldwide for a florbetaben histopathology study to date, said Dr. Sabbagh. The results show a strong correlation of tracer uptake to amyloid pathology, and the data support the value of florbetaben as a diagnostic marker for amyloid plaques. Florbetaben F18 was approved in the United States and the European Union as an amyloid-imaging agent after the study was completed. Three radiocontrast agents are now approved, and the Centers for Medicare and Medicaid Services ultimately may compensate physicians for florbetaben imaging, Dr. Sabbagh concluded.
—Erik Greb