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Hopes for better vCJD diagnosis Hopes for better vCJD diagnosis
(about 3 hours later)
Scientists are perfecting a technique which they hope will improve detection of mad cow disease (vCJD) in humans. 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.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 the test is not wholly reliable, and can lead to an incorrect diagnosis. 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.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.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.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. 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 and exposed to repeated rounds of ultrasound, which break the prions up into more numerous smaller particles. 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.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 testConfirmatory 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.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. 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 is that of 'false' positive results. He said: "One of the issues common to screening tests for various conditions is that of 'false'positive results.
"By developing a reliable confirmatory test, such as this one, the impact of these false positives can be minimised." "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."
There have been 161 deaths from variant CJD since the disease emerged in early 1990.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.The figure includes three people who received blood transfusions from donors who later developed the disease.