Variant CJD, the human form of BSE (or mad cow disease) first emerged in 1995. The disease, which affects the brain, is believed to have passed from cattle to humans through infected food. It causes personality change, loss of body function, and eventually death.
The research team from the MRC Prion Unit, based at University College London, working with the National Prion Clinic at the National Hospital for Neurology and Neurosurgery (NHNN) tested 190 blood samples, including 21 from individuals known to have vCJD. The blood test was able to detect blood spiked with a dilution of vCJD to within one part per ten billion – 100,000 times more sensitive than any other method developed so far.
Prions, the infectious proteins which cause vCJD and other fatal prion diseases, can inhabit a person’s body for up to 50 years before presenting symptoms. During this time there is a chance a carrier of vCJD infection could pass on the infection to others, for example through blood transfusion or even through surgical and medical instruments as prions can easily attach onto metal surfaces.
A widely available, accurate blood test would enable people to be diagnosed earlier and could also help identify carriers of the disease. This would help measure how widespread the prion infection is in the general population and identify those who are at risk of passing on the infection to others.
Lead author Dr Graham Jackson, Programme Leader at the MRC Prion Unit, said:
“This test comes at the end of many years of meticulous, painstaking research in our Unit and the NHS National Prion Clinic. Although further larger studies are needed to confirm its effectiveness, it’s the best hope yet of a successful early diagnostic test for the disease. 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.”
Professor John Collinge, Director of the MRC Prion Unit, said:
“One of the reasons that vCJD is such a dreaded disease and has caused such disruption and expense to health services is the lack of knowledge of who is and who is not a carrier of this infection. The next step will be to test anonymously several thousand blood donors from a country unaffected by BSE in order to gain a better idea of how the test fares in practice. Longer term studies will also be needed to assess what proportion of individuals who test positive for prion infection will then go on to develop the disease later in life.
“The MRC Prion Unit’s research with the NHS National Prion Clinic to improve early diagnosis is an essential part of the wider MRC strategy to develop better treatments for patients. For this to develop, it will be crucial for clinicians to be able to offer treatment before extensive irreversible damage to the brain has occurred. At the moment, a firm diagnosis of vCJD can usually be made only once serious symptoms of the disease have developed which indicate extensive damage to the brain.”
The study ’A blood-based assay for the detection of vCJD prion infection’ is published today in the journal The Lancet.
Notes to editors:
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1. For almost 100 years the Medical Research Council has improved the health of people in the UK and around the world by supporting the highest quality science. The MRC invests in world-class scientists. It has produced 29 Nobel Prize winners and sustains a flourishing environment for internationally recognised research. The MRC focuses on making an impact and provides the financial muscle and scientific expertise behind medical breakthroughs, including one of the first antibiotics penicillin, the structure of DNA and the lethal link between smoking and cancer. Today MRC funded scientists tackle research into the major health challenges of the 21st century. www.mrc.ac.uk
2. While the number of vCJD samples available for analysis was inherently small, and to date only a small number of healthy donors has been studied, analysis of this blinded panel indicated an assay sensitivity for vCJD of over 71% (15/21, CI 48-89%) and a specificity of 100% (0/169, CI 98-100%).
3. The NHNN forms part of University College London Hospitals NHS Foundation Trust, one of the largest NHS trusts in the United Kingdom providing first-class acute and specialist services. The Trust is committed to research and development and forms part of UCL Partners which in March 2009 was officially designated as one of the UK’s first academic health science centres by the Department of Health. UCLH works closely with UCL, translating research into treatments for patients. www.uclh.nhs.uk