Breakthrough in Alzheimer's fight

A super-sensitive test for Alzheimer's that could identify the disease long before symptoms appear has been demonstrated on patients, scientists have said.

The test is able to detect minute protein molecules called ADDLs which are thought to accumulate in the brain and trigger Alzheimer's.

Conventional tests are not sensitive enough to spot an ADDL, which stands for amyloid beta-derived diffusible ligand. The molecule is only five millionths of a millimetre (five nanometres) wide and present in cerebrospinal fluid at very low concentration.

Research suggests that ADDLs attack and disrupt synapses in the brain, the nerve cell connection sites vital to information processing and memory formation.

The process is thought to be reversible, opening up the possibility of early treatments that could halt the disease. As Alzheimer's progresses, hard lumps, or plaques, of amyloid protein form in the brain and impair its function.

William Klein, Professor of Neurobiology and Physiology at Northwestern University, Chicago, a member of the US research team, said: "Detection of plaques in patients may be too late. In the last three years, there has been a big effort in Alzheimer's research to identify and detect biomarkers in cerebrospinal fluid.

"We think the accumulation of ADDLs is likely to be the first biomarker in Alzheimer's disease, and now this extraordinarily powerful detection technology has changed what we think might be possible."

The scientists, whose findings appear in the journal Proceedings of the National Academy of Sciences, used the test to check the spinal fluid of 30 people.

ADDL levels in individuals who had been evaluated and shown to have Alzheimer's were consistently higher than those in a comparison group of healthy volunteers.

In future the researchers hope to develop a blood or urine test employing the technology, which relies on antibodies that home in on ADDL molecules.

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