Page last updated at 16:46 GMT, Friday, 6 February 2009

Test spots contaminated equipment

Contaminated equipment could spread vCJD

Scientists have perfected a highly sensitive test to detect vCJD-causing proteins on surgical instruments.

The test, which picks up the presence of prions on metal surfaces quickly and accurately, could help show whether decontamination processes are working.

Although there is no recorded case of a patient developing vCJD after surgery, experts say it is possible.

The test has been developed by the Medical Research Council Prion Unit at University College London.

Details are featured in Proceedings of the National Academy of Sciences.

As well as causing vCJD, prions are also responsible for a disease called kuru in humans, BSE in cattle and scrapie in sheep.

They are known to be able to survive conventional hospital sterilisation methods.

Professor John Collinge, director of the MRC Prion Unit, said: ''The presence of prions in blood and body tissues beyond the brain make many surgical and dental procedures a potential risk factor for transmission of prion diseases.

"Research has found that prions can withstand many sterilisation techniques, are very sticky and, when attached to a metal surface like a surgical instrument, are even more resistant to both chemical and heat treatments.''

Better than animal tests

The new test is much faster, and 100 times more sensitive than the existing test which involves injecting samples of suspect tissue into the brain of a mouse or hamster, and waiting for the animal to develop symptoms of disease.

It also makes it possible to test many samples at once at a relatively low cost.

The new test uses steel wires to enhance the sensitivity of a standard cell-based prion detection test called SCEPA (scrapie cell endpoint assay).

The prions present even in a very dilute sample bind tightly to the surface of the steel wires.

The wires are then covered with special cells that are very susceptible to prion infection.

After three days the prion-infected cells are harvested and prion concentration is measured using the standard cell-culture technique.

Professor Collinge said: "'That prions bind so readily to surgical steel is concerning but we have exploited this natural propensity of prions to develop a test that is so sensitive it can detect extremely low concentrations of prions in body tissues.'

"Finding a way to decontaminate delicate surgical tools to ensure they are free of prions is a public health priority."

Professor Collinge said the test had helped scientists to assess the effectiveness of new methods being developed to ensure surgical instruments are free from prions.

Using it had proved that enzyme solutions developed at the MRC unit were very effective sterilisation agents.

Professor Chris Higgins, chairman of the Spongiform Encephalopathy Advisory Committee (SEAC), said: "This test is a much more sensitive, cheaper and practical alternative to using mouse bioassays to detect prions."

He said the study would be considered at the next SEAC meeting.

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