Potential Diagnostic Tool for Early Alzheimer's Disease

APRIL 24, 2012
Alice Goodman
New Orleans, LA— Alzheimer’s disease (AD) is a suspected diagnosis that cannot be confirmed until death; autopsy or brain tissue biopsy is used to detect amyloid plaques or tangles, which are the hallmarks of this disease. A new study presented at the 2012 Annual Meeting of the American Academy of Neurology suggests that the drug florbetaben can be used as a biomarker with positron emission tomography (PET) imaging to diagnose AD by detecting amyloid plaques in the brains of living people suspected of having AD.
A global phase III trial was undertaken to compare brain regions in PET scans with respective brain regions from autopsy studies. Participants included those with suspected AD and those with no known symptoms of dementia. More than 204 participants who were near death offered to donate their brains for research; these patients underwent magnetic resonance imaging and PET scans with florbetaben. Ten healthy subjects also participated in the study. The amount of plaque in the brains of 31 participants who died and underwent autopsy was compared with the same regions of the brain imaged by PET scans.
A total of 186 brain regions from donors were analyzed along with 60 brain regions from healthy volunteers (246 brain regions in total). The presence or absence of beta-amyloid was determined by a panel of 3 neuropathologists. In the brain region comparison, florbetaben was found to detect beta-amyloid with a sensitivity of 77% and a specificity of 94%. Sensitivity refers to the percentage of actual positives that are correctly identified as positive, while specificity refers to the percentage of negatives that are correctly identified.
A comparison of visual assessment with florbetaben PET scans versus post-mortem diagnosis found that sensitivity of the florbetaben scan was 100% and specificity was 92%.
“This research confirms that florbetaben is able to detect beta-amyloid plaques in the brain during life with great accuracy and is a suitable biomarker. This is an easy, noninvasive method of assisting an AD diagnosis at an early stage,” said Marwan Sabbagh, MD, director of Banner Sun Health Research Institute in Sun City, AZ. He also stated that florbetaben may have a role as a research tool in studies of therapy designed to reduce beta-amyloid levels in the brain.

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