Questioning the Value of Mass Diabetes Screening Is Dangerous

Boris Hansel, MD


July 17, 2015

Today I'm going to talk about diabetes screening. [Editor's note: In the United States, it is estimated that there are presently 8 million diabetics who are unaware of their condition.][1] In France, the figure is 700,000. Why so many undiagnosed diabetics? The problem is certainly not that diagnosing diabetes is difficult because, as everybody knows, the diagnosis, in most cases, is based on a simple venous blood glucose measurement. What's more, the test is widely accessible. Rather, the problem is not enough hyperglycemia screening.

Who should such screening be proposed to? In other words, should every effort be made to detect hyperglycemia even before the onset of symptoms? If I'm addressing this question, which might seem naive, it's because the answers provided in the scientific literature are creating some confusion. To start, I'm referring to a recent review published in the Annals of Internal Medicine.[2] It summarizes a consensus statement by the USPSTF (US Preventive Services Task Force: Screening for Type 2 Diabetes Mellitus), which is made up of American experts. According to them, diabetes screening did not reduce mortality in a population followed for 10 years. Nonetheless, the authors state that treating prediabetes reduces the future risk of developing diabetes. Again, according to these experts, only individuals at risk should be screened, particularly those with hypertension.

Upon reading this report's conclusion, one gets the impression that mass diabetes screening should not be promoted—that, in the end, this would be of little value. I feel that such a message is dangerous because assessing the value of screening on the basis of the 10-year mortality rate is rather simplistic, primarily because the expected mortality benefits, particularly in patients with prediabetes or early diabetes, are long-term—well beyond 10 years. This, in fact, is what the UKPDS study found[3]: no mortality benefit during the 20 years of intervention. However, the benefit appeared when the data were reexamined 10 years later. Similarly, the Da Qing study,[4] in which dietary intervention was tested in prediabetics, showed a reduction in mortality—again, well after the study ended after 23 years of follow-up.

I find questioning the value of diabetes screening to be dangerous. The risk is to take screening lightly and, consequently, to delay diagnosing diabetes. A recent study published in Diabetes Care used a simulation to quantify the effects of delayed diagnosis.[5] A 6-year delay in diagnosis would increase the 10-year risk for cardiovascular events by 29%.

Another question: Is there a downside to proposing wide-scale diabetes screening? Presently, there is nothing to indicate that this is the case. One might be afraid to use treatments with an unfavourable risk-benefit ratio. This fear is absolutely groundless because the first-line treatment consists of dietary and lifestyle measures and because the pharmacologic intervention that would be indicated in the event of failure, if a diagnosis of diabetes is made, is metformin, whose safety has been demonstrated, including on a wide scale. Therefore, there is no reason to think that one should delay the start of treatment of hyperglycemia or that diagnosing hyperglycemia too early might be harmful.

So, in practice, I think it's reasonable to screen for hyperglycemia without setting down too many conditions. I think that the message should be simplified and that a blood glucose measurement should be proposed on a regular basis—for example, every 5 years in healthy adults. In France, this is, in fact, what is included in the free evaluations offered by the national health insurance scheme, but which is, in the end, done only in a minority of individuals. Of course, an annual blood glucose measurement is still indicated in people who already have risk factors—that is, overweight, hypertension, or dyslipidemia. The goal is simply to try to save at least some of the millions of diabetics who are unaware of their condition.


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