Finding holes in the brain: to test or not to test for Creutzfeldt-Jakob?

A new test for carriers of variant Creutzfeldt-Jakob disease is under development, but it raises an ethical problem: should we test for untreatable deadly illnesses? And might it reduce the amount of blood donations?

vCJD is due to a prion protein, a naturally occurring protein folded in such a way that the misfolded version causes the normal version to misfold. Over time this causes brain degeneration and eventual death. It is very slow-acting, possibly with a 50 year incubation time. CJD can be spread through blood products, tissue grafts, pregnancy and
(possibly) ingesting material from animals with the bovine form of the
disease. Classic CJD is very rare, about one case per million people per year and tends to occur in middle-aged people. The variant form strikes younger people and appears to act faster, but still has a very low incidence (167 people since 1990). But there are concerns that thousands in the UK could be harbouring the infection due to contaminated cattle in the late 1980’s and early 90’s

Testing for the disease in people can help screen potential donors to prevent infected blood transfusions (there has been four reported cases of transmission through transfusions in the UK). A survey last year suggested that there was support for testing from health professionals, researchers and other stakeholders. Testing could also help staff carrying out invasive surgery take precaution, but support for this was weak. They were also less certain the public should be given access to the test.

If donors are tested before donating blood, is there a risk that donations might plummet? (In a piece of journalism-friendly scaremongering the National Blood Service suggested "up to 50%") The logic would be that people would be fearful of donating blood since they could possibly be given a very negative news. While in theory the blood service could refrain from telling donors that they were positive and then throw away the blood, this is generally not regarded as ethical – it would waste resources, it would involve deceiving people about their health and it would actually be illegal. But current blood donors are tested for a range of diseases, including AIDS, which means that becoming a donor already runs the risk of giving bad news. Adding another disease to the test doesn’t seem to make it twice as scary. Even if donations might plummet, testing might be the right thing to do. As past cases with hepatitis C and HIV show, not introducing an available test can lead to litigation and perhaps rightful condemnation of not reducing a known risk when it can hurt innocents.

Another issue, regardless of whether testing is done among living donors, is whether deceased donors should be tested so that their blood could be withdrawn. This also raises the spectre of having to tell people that they might have been infected by donated blood or tissue, and whether to tell the family of the deceased. But since a single donor may affect many people adversely, it seems there is a strong reason to test.

How people take adverse test results is a big area of medical ethics, psychology and sociology. Some people take bad news in a stride, others are devastated by fear or feel stress because of the mere availability of a test – now they may have to make a potentially life-altering decision. Generally a discussion of the issues with the patient before giving the test is advisable. One issue is the lack of epidemiological data to inform discussion with
patients before a vCJD test. Since humans are generally bad at visualising
low probabilities "a chance in a million" may sound like anything from
zero to 99%.

Another problem with testing is that most tests can give both false negatives (not detecting infection) or false positives (claiming infection when there is none). Since vCJD is so rare, false negatives are not going to be a major issue. But even with a low rate of false positives many people will be given erroneous bad news (if there is a one in thousand chance of a false positive and a million people are tested, there will be about 1000 scared people and 1 person found with vCJD). Hence a reliable confirmatory test is going to be necessary.

It seems problematic to prevent interested people from testing themselves for whatever reason. As I have argued earlier in this blog, we have a far-reaching right to know about our own bodies and health. It is very hard to say anything general about what individual desires are right or wrong in regards to health. "The worried well" might waste money on tests that mainly make them nervous, but it seems unlikely that preventing them from testing for a particular condition is going to help them; at most it would save doctors a bit of annoyance – at the price of the very rare, but very loud, court case when somebody who "could have been saved" finds themselves ill. 

While there is no cure for CJD, a correct identification of the
condition can at least save much otherwise wasted or misdirected effort
on identification and treatment, enabling a focus on improving quality
of life. There is also the time aspect: while there is no cure today,
that may not be true in 10 or 30 years. Since the disease is so slow,
there is a decent chance that much useful medicine will be developed
before it strikes. This is a rational reason for hope – and to test.