Preclinical vCJD: prevalence higher than expected
Scientists last week expressed concern at the number of patients who could be incubating variant Creutzfeldt-Jakob disease and the risk of iatrogenic spread of the infection.
Researchers from Derriford Hospital in Plymouth, Imperial College in
London and the National CJD Surveillance Unit in Edinburgh published
findings from a study estimating infection. They tested stored appendix
and tonsil specimens taken from 1995—99, during surgery.
They found that three out of 12,674 samples showed lymphoreticular accumulation
of prion protein — a test thought to be indicative of vCJD.
The researchers say that, should their test be a reliable marker of preclinical
vCJD, the estimated prevalence will be 237 infections per million population. “This
will be of some concern as the prevalence is much higher than expected
from the observed incidence of clinical cases,” they add.
Although they describe several limitations to their techniques, they
say that the findings reinforce the importance of measures to reduce
the risk of spread of the disease via blood products and surgical instruments.
They also press for urgency to proceed with large scale screening of
fresh tonsil specimens for the presence of prion protein (Journal
of Pathology published online).
The Health Protection Agency is co-ordinating collection of 100,000 fresh
tonsil samples from routine tonsillectomies to estimate the population
prevalence of abnormal prion protein. Although
many samples will be from children who have not been exposed to possible
dietary causes of vCJD, the HPA says, at present, the samples should
include sufficient patients from older age groups considered most at
risk. However, the availability of tonsils from this cohort will diminish
over time. |
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