Test may improve Alzheimer's diagnosis.

Test may improve Alzheimer's diagnosis

Diagnosing Alzheimer's disease, the progressive neurological disorder, isn't easy, short of an autopsy. Relying on psychological testing, ruling out other disorders, and the identification of apparent abnormal brain growths that can not be verified until after death, physicians correctly diagnose the disease only about two-thirds of the time. But a new antibody test for a brain protein that only Alzheimer's patients appear to harbor may yield a more accurate and earlier diagnosis.

The protein, known as Alzheimer's disease-associated protein (ADAP), concentrates in brain areas that process and store memory. Researchers detected it in autopsied brain tissue from 48 (86 percent) of 56 people who died with Alzheimer's. In contrast, the antibody test found no ADAP in tissue from any of 27 people who died without nervous system impairment, or in 28 persons who had suffered other, unrelated neurological disorders, report Hossein A. Ghonbari of Abbott Laboratories in Abbott Park, Ill., and his colleagues in the June 6 JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION.

The team also detected ADAP in the spinal fluid of Alzheimer's patients, but in concentrations too low for the current antibody test to detect, says Ghonbari. He estimates that a more sensitive assay designed for spinal fluid likely will become available within two years, allowing detection of the telltale protein in living people without removing brain tissue. Ghonbari adds that the protein appears to precede structural nerve damage in Alzheimer's patients, indicating that ADAP may allow earlier diagnosis and earlier treatment.