This article is a review of literature up to February 2010 on the use of PIB-PET scans to detect amyloid protein in Alzheimer's, dementia with Lewy bodies, frontotemporal dementia, mild cognitive impairment, and cognitively normal people. Amyloid is one of the two key proteins involved in Alzheimer's disease. Amyloid is not part of "pure" DLB, where DLB occurs on its own. Most DLB co-occurs with Alzheimer's disease, in which case amyloid protein will appear.

The two things I learned from this abstract are:

* "Amyloid deposition appears to be an early event, and as dementia progresses clinical decline seems to be more associated with neurodegeneration than amyloid burden."

* "[Studies] have identified PIB-positive cases in otherwise healthy older individuals (10-30%), limiting diagnostic specificity." No wonder research in this field is such a challenge!

Robin




International Journal of Geriatric Psychiatry. 2011 Oct;26(10):991-9. Epub 2010 Dec 28.

PET imaging of brain amyloid in dementia: a review.

Quigley H, Colloby SJ, O'Brien JT.
Institute for Ageing and Health, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, UK.

Abstract
OBJECTIVE:
To review the rapidly expanding literature of amyloid PET imaging with particular attention to Pittsburgh compound-B (PIB) in Alzheimer's disease (AD), dementia with Lewy bodies (DLB), fronto-temporal dementia (FTD), mild cognitive impairment (MCI) and cognitively normal volunteers.

DESIGN:
Literature searches were performed using Medline up to February 2010. Individual articles were then examined for additional references not revealed by automated searches. This yielded 79 articles whose abstracts were read by the authors to select key papers.

RESULTS:
Amyloid deposition assessed using PIB-PET is significantly elevated in AD and DLB compared to controls and those with FTD.

In MCI, uptake is often intermediate between AD and normal ageing, and excessive amyloid burden in non-demented individuals with MCI are likely to represent high-risk cases.

Amyloid deposition appears to be an early event, and as dementia progresses clinical decline seems to be more associated with neurodegeneration than amyloid burden.

CONCLUSIONS:
PIB-PET imaging is a sensitive and specific marker for underlying Abeta amyloid deposition and represents an important investigative tool for examining the relationship between amyloid burden, clinical symptoms and structural and functional changes in dementia.

Amyloid imaging may also be useful for selecting patients for anti-amyloid therapies. However, studies have identified PIB-positive cases in otherwise healthy older individuals (10-30%), limiting diagnostic specificity.

Development of biomarkers for investigating other aspects of dementia pathology, i.e. soluble Abeta, tau, synuclein and brain inflammation would further inform our understanding and assist in studying disease-modifying and preventive treatments in dementia.

Copyright © 2010 John Wiley & Sons, Ltd.

PubMed ID#: 21905095 (see pubmed.gov for this abstract only)

Back to the drawing board, eh?