MD Stein - Who Has Diabetes? It's Hard To Know Anymore
Do you have diabetes or don’t you? It’s hard to know if you don’t have the classic symptoms of high blood sugar (frequent urination, blurry vision, constant thirst). For the asymptomatic, the diagnosis is based on blood tests, the values of which are constantly being updated. The thresholds used to define abnormal keep changing, and new questions about clinical care keep arising.
The World Health Organization proposed the first definition of diabetes based solely on laboratory testing in 1965. By 1979, the lab test utilized in this initial definition was outdated and a single fasting blood test (glucose level >140) was now “diabetes.” In 1997, this diabetes glucose threshold was again lowered to >126, instantaneously increasing the number of diabetics in the country
Around the same time, new terms such as “impaired fasting glucose” or “pre-diabetes,” were introduced, identifying persons whose glucose control was not quite “normal,” but not quite diabetic. In 2003, this “pre-diabetes” cut-off number was lowered as well, further increasing the number of Americans worried about and monitored for sugar-related abnormalities. Diabetics were said to have a slightly higher risk than pre-diabetics of developing the most common complication of elevated blood sugar—retinopathy or eye damage—but at the borderline between these two classifications, the risk difference was minimal.
In the last year, the American Diabetes Association (ADA) made things even more complicated. In addition to the fasting glucose concentration, they suggested that a hemoglobin A1C result (a more convenient blood test that does not require fasting and is not affected by recent changes in diet or activity) could now be used to diagnose the disease.
This has meant that there are now several different groups of people with abnormal blood sugar tests: One that has an abnormal fasting glucose, but a normal A1C; one that has an abnormal A1C but a normal fasting glucose; and one that has both abnormal A1C and fasting glucose levels. Are they all equally diabetic? Is one group at greater risk for eventual complications? Do we treat them the same way?
Add to these questions the difficulty of choosing a single cut-point in a lab test, whether its fasting glucose or A1C, that we use to define disease. Such choices are inevitably arbitrary, always contentious, and in the end made using best available evidence and consensus.
If there were no ADA, we would define a normal (healthy) fasting glucose or A1C value as any result that fell within the middle 95% of the millions of blood sugar tests values reported each year by labs in this country; that’s the standard definition of what “normal” is for any blood test. But the ADA is an advocacy group. It doesn’t accept this statistical conception of normal, but promotes instead a more difficult to achieve target for acceptable values, one they would call the “clinically desirable” range. But as we’ve seen, what’s clinically desirable changes, thresholds evolve, and we all get confused about who has diabetes or pre-diabetes and what it all means. Still, these definitions matter: they impact employment, insurability, and whether one is recommended for medication use.
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