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Hopes rise for test to spot vCJD

October 09, 2002

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A SCREENING test for vCJD, the human form of mad cow disease, could one day ensure no one gets the disease from donated blood.
More than 100 people have succumbed to the disease, mostly in Britain. The risk that it could be spread through transfusions (see below) has led the US to stop accepting blood donations from anyone who has been in Britain.
The new screening system, under development in Germany, could distinguish infected from healthy blood in as little as 15 minutes. When tried out on blood from hamsters infected with scrapie - a disease similar to mad cow disease (BSE) and vCJD - the test picked up 97 per cent of all infected samples, with no false positives for for healthy blood.
"At present, we are trying to extend the system to the serum of BSE-infected cows," says Dieter Naumann at the Robert Koch Institute in Berlin, whose team developed the system. Next, he hopes to develop tests that would detect vCJD-infected human blood.
What makes the approach unusual is that it doesn`t look for prions, the misshapen proteins that cause the diseases. Other teams have focused mainly on antibody-based systems designed to detect prions directly. Instead, the test picks up subtle differences in the overall chemical make-up of infected and healthy samples, just as we can tell smells apart without having to know which chemicals are involved.
Naumann`s team first subjects the blood to a form of chemical analysis called Fourier transform infrared spectroscopy, which generates spectral peaks and troughs depending on how much infrared radiation of varying frequencies a sample absorbs.
By training neural computer networks to link illness with the fine detail of these spectra, the team can make the system distinguish between scrapie-infected samples and healthy hamster blood. "If we get serum from vCJD patients and healthy controls, we will try to train a corresponding neural net [for people]," says Naumann.
"The proposed test can be completely automated and potentially requires less than 15 minutes for taking the sample, acquiring the spectrum and attaining the final diagnosis," the team says in Analytical Chemistry (vol 74, p 3865).
There is still a long way to go to achieve this. But if the test is adopted by hospitals, it could pose a tricky ethical question. At the moment, donors to Britain`s National Blood Service sign a form agreeing to be told of any conditions discovered, such as HIV. But should people be told they have an incurable brain disease?

Author: Andy Coghlan

http://www.newscientist.com">New Scientist issue 12 OCTOBER 2002


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