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Variant CJD

 

Clinical bottom line

A study that found variant CJD prion protein in one tonsil specimen in 8,318 tonsil and appendix samples examined in people aged 10-50 years has very wide confidence to estimate prevalence. The 95% confidence interval was 0.5/million to 900/million. About 20 cases a year have been seen in the UK in recent years.


Reference:

DA Hilton et al. Accumulation of prion protein in tonsil and appendix: review of tissue samples. BMJ 2002 325: 633-634.

Study

Appendix and tissue samples from patients aged 10-50 years from histopathology departments across the UK were retrieved for testing for prion protein. Most samples were appendixes and most were from people aged 20-29 years.

Results

One positive case was found in 8,318 tested. The estimated prevalence was 120 per million, but with wide confidence interval of between 0.5 per million to 900 per million. Positive results were found in 19 of 20 appendixes removed at autopsy from cases of variant CJD.

Comment

It is possible that some positive cases could be missed, but the absolute number of positives was low. The wide confidence interval, if applied to the UK population of about 50-60 million (depending on any arbitrary age cut-off), would imply a total number of cases of between 30 and 54,000.

Figures for cases of variant CJD and sporadic CJD taken from the regularly updated UK website (www.cjd.ed.ac.uk/figures.htm) in October 2002 show about 20 cases a year over the last five years (Figure 1). For 2002 deaths and affected cases were taken together.

Figure 1: Sporadic and variant CJD in the UK

While none of this leads to any confident conclusion given the unknowns and uncertainties over this disease, the current rate of cases give hope that the prevalence is at the lower end of the confidence interval.