Blood test for vCJD 'could identify carriers'

Brain scan of a patient with variant CJD, the yellow areas are diseased

A blood test for variant CJD has been developed by British scientists.

Currently patients suspected of having the human form of BSE have to undergo a series of tests, including a brain biopsy, to confirm a diagnosis.

The new test, reported in The Lancet, offers the chance of earlier diagnosis and potentially the ability to screen donor blood.

But further studies are needed before it can be widely used to screen healthy people who may be silent carriers.

Variant CJD or vCJD is the human form of BSE - "mad cow" disease. It affects the brain and is believed to have passed from cattle to humans through infected food.

There have been 170 confirmed deaths from vCJD in the UK, but a previous study suggested one in 4,000 Britons could be incubating the incurable degenerative disorder without symptoms.

CJD causes the brain to develop a spongy texture known as spongiform encephalopathy.

Early symptoms include anxiety, depression and tingling pains. Doctors often do not realise that a patient has the brain condition until other features occur, such as difficulty with movement, or loss of mental abilities.

At present, there is no treatment for variant CJD and the diagnosis is often made when patients are terminally ill.

The new test was tried on 190 blood samples, of which 21 had variant CJD. The test picked up 15 of the samples with variant CJD - a 71% success rate.

It did not produce any "false positives" - showing that someone had CJD, when they did not.

Early diagnosis

Professor John Collinge of the Medical Research Council is one of the doctors involved in the research. He said that he would begin using the new test on patients in his clinic straight away.

He said: "An earlier diagnosis will give patients and their families more time to plan what they would like to do in the time left available to them."

Professor Collinge is currently working on research to treat the disease with antibodies.

He told the BBC that the first clinical studies involving patients could be carried out as early as next year.

A test that provides an early diagnosis will become even more significant if treatments for the disease become available.

The development was welcomed by Peter Mills, whose daughter Holly was diagnosed with variant CJD in 2003.

He described the test as milestone, saying: "This lifts us into the next stage and takes us to a position of hope. It gives us great confidence that therapies to treat the disease are a realistic prospect - but this test has to come first."

Silent carriers

The new test could provide more information on how many people have variant CJD and be used to screen for the disease.

However, further large scale studies on populations where the disease is not present would be needed before it could be used as a screening test.

The lead author of the research, Dr Graham Jackson of the Medical Research Council's Prion Unit, said: "This test could potentially go on to allow blood services to screen the population for vCJD infection, assess how many people in the UK are silent carriers and prevent onward transmission of the disease."

Patients and their families can find out more about the new development by looking at the National Prion Clinic website.

Chris James, from the Haemophilia Society said they would push for the test to be used as soon as it is clinically available: "The Haemophilia Society has long called for tests to be offered, in combination with pre and post-test counselling, to people with bleeding disorders who have been told they are at risk for public health purposes in relation to vCJD."