Summary results of the second national survey of abnormal prion prevalence in archived appendix specimens August 2012
Posted Aug 13 2012 11:14am
Summary results of the second national survey of abnormal prion prevalence in archived appendix specimens
In April 2008, the Spongiform Encephalopathy Advisory Committee (SEAC) considered available prevalence data for variant Creutzfeldt-Jakob Disease (vCJD) in the British population and advised that a second appendix survey, using the same approach as a previous appendix tissue survey  on samples from the 1941 to 1985 birth cohort, be undertaken to further refine the estimate for the prevalence of subclinical infection .The second unlinked anonymous survey of the prevalence of abnormal prion protein in archived appendix tissues has now been completed and this summary provides an update to the interim results published in September 2011 [3,4].
The survey examined appendices by immunohistochemistry from operations conducted between 2000 and 2012 and collected from 41 hospitals throughout England. Abnormal prion accumulation was detected within the follicular dendritic cells of 16 appendices out of 32,441 suitable samples examined. None of the positive appendices have come from the 176 known vCJD cases in the UK. In line with the interim findings, the final overall prevalence estimate, 493 per million (95% Confidence Interval (CI): 282 to 801 per million), remained statistically consistent with results from the earlier appendix survey (237 per million, 95%CI 49 to 692 per million) which examined samples from operations performed between 1995 and 1999 . The prevalence estimates by birth cohort were 733 per million (95% CI: 269 to 1596 per million) in those born between 1941 and 1960 and 412 per million (95% CI: 198 to 758 per million) in those born between 1961 and 1985: these results were also in line with the interim findings [3,4].
The survey was conducted by a collaboration of the HPA, the Department of Neurodegenerative Diseases at the UCL Institute of Neurology, the Animal Health and Veterinary Laboratories Agency, the National Creutzfeldt-Jakob Disease Research and Surveillance Unit, the Histopathology Department of Derriford Hospital in Plymouth, and the MRC Prion Unit.
The final survey results have been considered by the Transmissible Spongiform Encephalopathies Risk Assessment Sub-Group of the Advisory Committee on Dangerous Pathogens, the successor to SEAC . In summary, the estimated prevalence range largely overlaps that from the first survey, but is narrower with a higher central estimate (around 1 in 2000 compared with around 1 in 4000). The new survey also demonstrates the presence of prion protein across a wider birth cohort than previously.
The hypothesis that the prevalence of abnormal prions found in both appendix surveys to date is linked to the epidemic of BSE in cattle in Britain can be tested directly by studying further appendix samples archived prior to the BSE outbreak and samples from those born in 1996 or later by which time measures had been put in place to protect the food chain .
1. Hilton DA, Ghani AC, Conyers L, Edwards P, McCardle L, Ritchie D, et al. Prevalence of lymphoreticular prion protein accumulation in UK tissue samples. J Pathol 2004; 203: 733-9.
2. Spongiform Encephalopathy Advisory Committee (SEAC). Position Statement. Prevalence of subclinical variant Creutzfeldt-Jakob Disease infections. August 2008. SEAC position statement.
5. Advisory Committee on Dangerous Pathogens (ACDP) TSE Risk Assessment Subgroup. Position Statement on occurrence of vCJD and prevalence of infection in the UK population. July 2012. Available at: http://www.dh.gov.uk/ab/ACDP/TSEguidance/DH_125868 .
considering this study was only looking at the appendix, was only using immunohistochemistry, this study tells little, and may even be giving false hope.
in my opinion, everyone in the U.K., back in the worse days of the mad cow epidemic, that consumed beef, would have had to have been exposed to BSE, how many there from that are sub-clinical, that is another question, one this study does not answer in full.