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Test gives early alert on Alzheimer's disease: An American advance raises hope that people at risk can be detected sooner. James Cusick reports

A ROUTINE diagnostic test for Alzheimer's disease, the premature degeneration of brain cells characterised by memory loss, will be patented in the United States next week. The test, developed by Dr Daniel Alkon, a neurophysiologist, will end the costly and lengthy process of trying to diagnose the disease by clinical means only.

Although this test can only identify the disease once it is established, there are hopes that tests can be developed to identify those at risk of Alzheimer's. Up to 500,000 people in Britain have the disease. Precise details of the research at the National Institute of Health are being held back until the formal launch of the patent in the US next week. However, on the first day of the International Union of Physiological Sciences congress in Glasgow, Dr Alkon said research on how simple creatures such as molluscs had stored information in their limited memory had formed the foundation of the work at the NIH.

Over the past eight years, Dr Alkon has pioneered the detective work in identifying the series of molecular events needed for an organism to develop a memory record. The Alzheimer's test has come since the research has moved on to study the memory of mammals.

Dr Alkon described the human brain as like a complex wiring circuit 'with millions of neurones and trillions of synapses' - the communication junctions between nerve cells. The key to the new test is that in Alzheimer's sufferers, where memory has degenerated, part of the body's circuitry involved in the memory process is missing. The missing or malfunctioning area affected centres on one of a number of 'potassium channels', which are critical to the ability to store and retrieve information. In people diagnosed as having Alzheimer's, activity in one of the body's 15 or 20 potassium channels is absent. The test will be the first laboratory diagnosis of Alzheimer's, which has until now relied on lengthy and imprecise clinical evaluation. Dr Alkon said that he hoped 'prediction techniques' would now evolve.

In another study to be highlighted at the congress, the body's production of nitric oxide could throw light on the processes involved in the disease.

Recent research shows that nitric oxide, normally regarded as a pollutant outside the body, acts inside as a chemical signal to control other functions. In the brain, where cell communication is the basis of memory and learning, it is now believed that defective nitric oxide production may be involved in Alzheimer's.

A team led by Dr Eric Flitney from the University of St Andrews will also outline findings that show that drugs which impair nitric oxide production can slow rates at which cancers grow. Other new research to be delivered at the congress, which runs until 6 August, includes how the use of super- computers is helping to understand the human heart, and advances in the understanding of cystic fibrosis.

How new blood vessels grow, how the cells that line blood vessels work, and how new drugs can block blood vessel growth, will also be discussed at a two-day symposium. The new drugs are potent inhibitors of the growth of solid tumours because cancer cells need blood vessels to survive.