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Last Updated: Thursday, 5 July 2007, 09:06 GMT 10:06 UK
Hopes for better vCJD diagnosis
Prion tissue
Prion diseases affect the brain
Scientists are perfecting a test which they hope will confirm mad cow disease (vCJD) in humans.

At present doctors test for the presence of abnormal proteins called prions which are thought to cause the disease by killing off brain cells.

But this can only be definitively done at post mortem by examining the brain.

An Edinburgh University team has found a way to boost prion numbers to confirm a diagnosis. Their work features in the Journal of Pathology.

The technique, known as protein misfolding cyclic amplification (PMCA), works by by mimicking and accelerating the replication of prions so they are more easily detected in test samples.

It has so far been tested mainly in animal models.

But the Edinburgh team has shown for the first time that it is possible to use the technique to amplify the number of vCJD prions in infected human brain tissue extracts by using normal blood cells (platelets) to drive the reaction.

The sample is incubated with platelets and exposed to repeated rounds of ultrasound, which break the prions up into more numerous smaller particles.

Further research is needed to establish whether the technique can be applied to other tissues, such as blood, that might be used in tests for vCJD.

Confirmatory test

Professor James Ironside, of Edinburgh University's National CJD Surveillance Unit, said the test took too long to carry out to be used to obtain a rapid diagnosis in a blood donation centre.

But he said it could well be suitable as a confirmatory test that could be conducted at a national centre on patients suspected of having the disease.

He said: "One of the issues common to screening tests for various conditions is that of 'false'positive results.

"Work is currently ongoing to develop a screening test for vCJD. By developing a reliable confirmatory test, such as this one, the impact of these false positives can be minimised."

Roger Tomkins, of the CDJ Network, which offers support and advice, said: "We all believe that the earlier the diagnosis the better.

"We know there is no cure but it would save an awful lot of unnecessary and regretful treatment.

"That, for me, would be the real breakthrough."

There have been 161 deaths from variant CJD since the disease emerged in early 1990.

The figure includes three people who received blood transfusions from donors who later developed the disease.


SEE ALSO
Scientists 'reverse' vCJD signs
01 Feb 07 |  Health

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