Alzheimer's disease is the most common form of adult onset dementia and is characterized by the degeneration of the nervous system. In particular, as the disease progresses, the amount of amyloid-ß peptide in the body rises. At present, the most reliable and sensitive diagnostic techniques are invasive, e.g. require analysis of cerebrospinal fluid (the liquid that surrounds the brain and spinal cord). However, white blood cells (or mononuclear leukocytes) are also thought to carry amyloid-ß peptide in Alzheimer patients.
The researchers used two-dimensional infrared spectroscopy to measure and compare the infrared radiation emitted or absorbed by white blood cells of healthy controls, versus those of patients with mild, moderate and severe Alzheimer's disease. A total of 50 patients with Alzheimer's and 20 healthy controls took part in the study and gave blood samples.
The authors found significant differences in the range of infrared wavelengths displayed between subjects, which were attributable to the different stages of formation of amyloid-ß structures in the blood cells. The results showed that, with this method, healthy controls could be distinguished from mild and moderate sufferers of Alzheimer's disease. The method is being explored as a tool for early diagnosis.
The authors conclude: "The method we used can potentially offer a more simple detection of alternative biomarkers of Alzheimer's disease. Mononuclear leukocytes seem to offer a stable medium to determine ß-sheet structure levels as a function of disease development. Our measurements seem to be more sensitive for earlier stages of Alzheimer's disease, namely mild and moderate."
Carmona P et al (2012). Infrared spectroscopic analysis of mononuclear leukocytes in peripheral blood from Alzheimer's disease patients. Analytical and Bioanalytical Chemistry; DOI 10.1007/s00216-011-5669-9