Telltale signs

2019-03-08 04:01:01

By Debora MacKenzie in Brussels A ROUTINE diagnostic test for Alzheimer’s disease has been licensed for use by doctors. Innogenetics, a biotechnology firm in Ghent, Belgium, says its test picks up early signs, which should allow treatment once new drugs for the disease become available. Early Alzheimer’s can be difficult to distinguish from other mental problems of old age, caused by stroke, for example, or neurodegenerative diseases. The new test relies on an antibody that recognises tau, a protein involved in intracellular transport. In Alzheimer’s patients, tau is covered with too many phosphate groups, forming tangled fibrils in the brain that may contribute to dementia. Looking at these microscopic brain structures after death is currently the only way to confirm an Alzheiner’s diagnosis with certainty, although some memory tests can hint at the disease (This Week, 2 August 1997, p 6). Levels of tau increase in the cerebrospinal fluid (CSF) very early in the disease, says Eugeen Van Mechelen of Innogenetics. CSF is easy to get at by using a needle to draw it off from the spine. Alzheimer’s tests based on other proteins in CSF have been available to researchers for several years, but Innogenetics is the first to register a test for routine diagnosis. Michel Goedert of the MRC Laboratory of Molecular Biology in Cambridge cautions that other conditions, such as stroke, can also raise levels of tau. But Van Mechelen argues that these conditions have different symptoms. “Clinical symptoms must always be considered along with the test,” he says. Five per cent of Alzheimer’s patients show normal levels of tau, but Innogenetics is developing a supplementary test for beta-amyloid protein,