By Michael Day STORED samples of tissue from removed appendixes may at last shed some light on the risks posed to the British population by vCJD, the new variant of Creutzfeldt-Jakob disease that is thought to be the human form of BSE. But experts warn that the tests may raise more questions than answers. In the latest issue of The Lancet (vol 352, p 703), a team led by David Hilton of the Derriford Hospital in Plymouth reports the case of a man who developed symptoms of vCJD eight months after having his appendix removed. Tests on the organ showed that it contained large quantities of the prion protein thought to cause vCJD. A team led by neuropathologist James Ironside of the CJD Surveillance Unit in Edinburgh will now test thousands of removed appendixes, which are routinely held in pathology laboratories, to try to gauge the number of people incubating vCJD. They will also test tonsils, which might harbour the prions. But the researchers warn that the study will be fraught with uncertainties. “If we look at 2000 samples and find nothing, this offers us very limited assurances,” says Peter Smith of the London School of Hygiene and Tropical Medicine. If one or two positive samples are found in a sample of 1000, this would suggest that tens or even hundreds of thousands of people are infected. But scientists still wouldn’t know how long it would take for symptoms to develop. Smith adds that some people whose appendixes or tonsils test positive might never develop vCJD. Prions could accumulate in these organs as a result of eating sheep infected with scrapie, a related disease, he says. Nevertheless, the team will assume that a positive result does mean that a person is at risk of developing vCJD. But any positive results in the anonymous screening will raise an ethical dilemma: should appendicectomy patients be tested and told of positive results?