New Technique Could Be Useful In the Early Detection of Alzheimer's

A diagnostic technique which may greatly simplify the detection of Alzheimer's has been discovered by researchers. A new technique called near-infrared (NIR) biospectroscopy was able to identify changes in oxidative stress levels in blood plasma, which could be useful in the early detection of Alzheimer's. There is currently no accepted laboratory test for diagnosing Alzheimer's.

The image depicts the comparison of a normal aged brain (top) and an Alzheimer's patient's brain (bottom). Differential characteristics are pointed out.

Researchers have shown that NIR biospectroscopy can identify a chemical signature, or biomarker, in blood that distinguishes Alzheimer's from normal aging and possibly other neurodegenerative conditions. Diagnosis of Alzheimer's is currently based solely on a patient's medical history and neurological examination, is labor-intensive and expensive, and often inconclusive in early stages of the illness. The availability of a biologic marker that reliably differentiates Alzheimer's from normal aging and other dementia would represent a major achievement in the management of this common neurodegenerative disorder.

"There is an urgent need for an accurate diagnostic test to aid in the early diagnosis and management of Alzheimer's," said Hyman M. Schipper, lead author of the study. "Our observations give us hope that biospectroscopy will offer a new approach to the early diagnosis of Alzheimer's and other neurodegenerative disorders."

In this study, an NIR biospectroscopy analysis was conducted on blood plasma samples from a total of 63 subjects, 19 with Alzheimer's, 27 with mild cognitive impairment (a frequent indication of Alzheimer's) and 17 normal elderly controls, to measure the degree of oxidative stress in plasma. Oxidative stress is caused by a chemical imbalance that can damage critical components of cells and biofluids, including proteins, lipids and DNA. Oxidative stress is known to be involved in many neurological diseases, including Alzheimer's and Parkinson's disease.

In differentiating Alzheimer's patients from the normal elderly control group, NIR achieved a sensitivity of 80% and specificity of 77%. Fifteen and twelve patients with mild cognitive impairment were classified with the normal elderly control group and Alzheimer's groups, respectively.

The researchers were able to distinguish Alzheimer's from healthy controls with 80 per cent sensitivity (correct identification of patients with the disease) and 77 per cent specificity (correct identification of persons without the disease). A significant number of subjects with mild cognitive impairment tested positively with the Alzheimer group, indicating that the test may be capable of detecting Alzheimer even before patients' symptoms meet clinical criteria for dementia.

"These results demonstrate the potential for NIR biospectroscopy to differentiate mild, and possibly pre-clinical, Alzheimer's from normal aging with high accuracy," Dr. Schipper added. "We are very encouraged by these data and look forward to testing this potential diagnostic tool in larger-scale studies. The advent of a simple blood test for the diagnosis of early Alzheimer's would represent a major achievement in the management of this common disorder"

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References:
1. Hyman M. Schipper, et al. Near-Infrared Spectroscopy of Blood Plasma for Diagnosis of Sporadic Alzheimer Disease. Journal of Alzheimer's Disease, 17:2 (June 2009).