Medicalising the healthy: is ‘pre-diabetes’ a useful term?

Diabetic injecting insulin
There are more than 3 million people with diabetes in Britain. Photo: Alamy

Diabetes is the great modern scourge. More than three million people suffer the disease in this country. The NHS says that about 10 per cent of its budget, roughly £10 billion a year – £27 million a day – is spent treating it and its complications – including but not limited to blindness, kidney stones, nerve damage in the extremities, and the tissue death and amputation of those extremities. The indirect costs to the country, from absenteeism, disability, care requirements and death, come to a further £14 billion. It is a blight, a plague; what’s more, it’s a plague created by our lifestyles. Too much sugar, too much salt, too much fat; the obesity epidemic has sparked the diabetes one.

What’s more, the situation is likely to get worse. One study predicted that the costs would rise disproportionately in the coming years, perhaps 17 per cent of the NHS budget by 2035. Forecasts like this are always to some degree guesses, and suggestions that it will bankrupt the NHS are probably hyperbolic, but it is no exaggeration to say that diabetes is a huge and growing problem for health care in this country. One partial fix, of course, might be if we were able to identify those most at risk of developing the disease. And that already happens. Diabetes is a disease of blood sugar – the body cannot produce enough insulin, a hormone which tells cells to suck glucose out of the bloodstream, and the high levels of sugar in the blood start to damage organs. So patients with a higher level of blood sugar are sometimes defined as “pre-diabetic”; an at-risk group.

Prevention is better than cure; it’s one of the great truisms. Prevention is certainly cheaper than cure in most situations. But all screening programmes like this come at a significant cost: they involve telling a large number of essentially healthy people that they have a disease.

The classic example is breast cancer. Imagine that the test for breast cancer is 90 per cent accurate: if a woman doesn’t have breast cancer, the test will correctly say so nine times out of 10. (Let’s not worry, for the moment, about the risk of it missing someone who does have cancer.) The “false positive” rate is one in 10. So if you go for a cancer screening, and your result comes back positive, you’re 90 per cent likely to have breast cancer, right?

No – you’re not. If you’re a 40-year-old woman, your odds of having breast cancer are about one in 70. So if 70 women are screened, there will on average be one woman with cancer – and seven false positives. If you have had the test, and it’s come back positive, there’s still only a one in eight chance that you actually have cancer. Seven women will spend several terrifying weeks undergoing follow-up tests only to be told, eventually, that it was all a false alarm.

That’s not to say that screening is without value: you’ve gone from a one-in-70 chance to a one-in-eight chance of having the right person, and that’s a very useful thing from a clinical point of view. But there is a price to be paid for that information, and that price is paid by the population.

With “pre-diabetes”, there is a similar but opposite problem: while pre-diabetic people are at greater risk of diabetes, if you are diagnosed as pre-diabetic under current guidelines, you still have a less than 50 per cent chance of actually developing the disease. The American Diabetic Association (ADA) has expanded its definition of pre-diabetes; under their criteria, barely one person in 10 would go on to get full-blown diabetes. Their criteria would call 18 million people in Britain – nearly a third of the population – pre-diabetic. This has led to John Yudkin, an emeritus professor of medicine at UCL, writing in the BMJ, that it is time to drop the pre-diabetes diagnosis altogether, because it is essentially useless as a clinical tool.

I’ve spoken to a couple of public health specialists, and say that Yudkin is right that this test is pretty much useless as a clinical tool, but as a public health measure, it might be more effective. Obviously hugely scaring nine people in the hope that it will stop the 10th getting diabetes is not a good thing – but if the risks can be expressed sensitively, then it might be the case that this could act as a sort of early warning system, allowing doctors to tell patients that they are at risk, and that it would be a good idea to change their lifestyle. Since the steps taken to avoid diabetes – better diet, more exercise – are the same as the steps taken to get healthier in general, that could be useful. Diabetes UK supports the use of the term, and the ADA’s criteria, as a weapon against the rise of diabetes in this country.

In his BMJ piece, Yudkin tellingly quotes Aldous Huxley: “Medical science has made such tremendous progress that there is hardly a healthy human left.” There is something worrying about a diagnostic tool that labels one person in three unhealthy, especially when 90 per cent of those people will be fine. On the other hand, there may be a public health benefit from using that tool. Whether the cost in public alarm is worth the gain is not a question I can answer for you.

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