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Several new studies on Alzheimer's disease raise hope for new treatments and offer an understanding of disease progression. Here's a look at a few.
- By measuring cerebrospinal fluid concentrations of amyloid beta42 peptide and tau protein, researchers at the University of Pennsylvania say they have devised a test capable of confirming or ruling out Alzheimer's disease. The authors of the study published in the online edition of the Annals of Neurology were able to identify AD at the earliest stages, before dementia symptoms appeared and extensive irreversible damage occurred. For the study, CSF was collected from 410 volunteers from 56 sites across the US and Canada. CSF samples taken from 56 people with confirmed AD based on post-mortem autopsy diagnosis were also measured to establish threshold values for these biomarkers.
Measured against normal, healthy adults of the same age, a pattern of changes materialized in people with MCI or AD. Tau concentrations increased while amyloid beta42 levels decreased as the disease progressed.
Overall, the test was 87 percent accurate. The test accurately ruled out AD in 95.2 percent of subjects. It positively predicted the conversion from MCI to AD at a clip of 81.8 percent. In the CSF samples from the post-mortem-confirmed AD patients, the amyloid beta42 concentration threshold was most sensitive and revealed AD at nearly a 97 percent rate. - A high-density genome-wide analysis of participants in the Alzheimer's Disease Neuroimaging Initiative (ADNI) is more than 95 percent complete. The ongoing $60 million project involves MRI and PET brain imaging and blood, urine and spinal fluid biomarker studies of more than 800 people, half of whom have MCI. The primary goal of ADNI is to "determine whether brain imaging, other biological markers, and clinical and neuropsychological assessment can accurately measure the progression of MCI and early AD." All data are available to qualified investigators through www.loni.ucla.edu/ADNI.
- Losing brain cells in the hippocampus is associated with a higher probability of developing dementia, according to a study published in Neurology (72: 999-1007). Researchers followed 64 people with AD, 44 with MCI, and 34 with no memory or thinking problems. MRI scans were performed on all participants at baseline and again a year and a half later, on average, to measure the volume of the whole brain and the hippocampus area and calculate the rate of shrinkage over time. Twenty-three people with MCI developed AD, along with three other healthy participants.
For participants who did not have dementia at the start of the study, "those with smaller hippocampal volumes and higher rates of shrinkage were two to four times as likely to develop dementia as those with larger volumes and a slower rate of atrophy." - A new generation of molecular imaging agents called Avid AD-45 and a high sensitivity, experimental research PET brain scanner named NeuroPET are being studied to scan amyloid plaque. Ideally, high sensitivity will provide high quality brain scans using lower doses of radioactive agents, allowing patients to undergo more frequent diagnostic scans to monitor response to therapy.
Investigational radioactive "tracer" chemicals connect inside the brain to markers for specific diseases, such as AD or Parkinson's, coupled with high tech scanners that produce 3-D images of these disease-specific diagnostics distributed within the brain, according to Avid Radiopharmaceuticals, one of the product developers.
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