Two Promising Diagnostic Tests to Detect Alzheimer's Disease in its Early Stages

Alzheimer's disease

Non-invasive tests of the human eye could someday lead to early indicators of devastating Alzheimer's disease

Brigham and Women's Hospital's (BWH) Lee Goldstein, MD, PhD, in one of the most promising sessions at the 89th Optical Society of America Annual Meeting, presented information about two optical tests that could someday be used to diagnose Alzheimer's disease in its early stages - a disease in which early screening tests continue to elude scientists. These tests may not only improve patients' chances to start treatment earlier, but they could also speed development of new Alzheimer's drugs.

Goldstein and colleagues have developed two tests that have grown out of recent stunning findings that Alzheimer's disease can be detected early by looking for amyloid beta proteins - a hallmark of Alzheimer's disease found in the brain - in the lens of the eye and its surrounding fluid. The researchers also discovered that the amyloid beta proteins in the lens produce a very unusual cataract, formed in a different place in the eye than common cataracts (which are not at all associated with Alzheimer's.

Details of the two tests include:

• Using a technique known as quasielastic light scattering, the first test employs low-power infrared laser light to noninvasively detect protein particles in the specific part of the lens where these unusual cataracts form.

• The second test would be applied to those who screen positively for the proteins, in order to confirm an Alzheimer's diagnosis. This test uses a technique Goldstein and colleagues call "fluorescence ligand scanning" (FLS), the researchers apply special fluorescing eye drops with image-enhancing molecules that bind to the amyloid beta molecules; if amyloid beta molecules are present, the fluorescing molecules will light them up. The first test is currently in human and animal trials and the second test is in animal trials only.

According to Goldstein, these two technologies could someday be used to develop new tests for rapidly detecting amyloid plaques resulting from prion diseases, including mad cow, scrapie in sheep and Creutzfeldt-Jacob disease in humans.