In my last 2 entries (June 8 and June 11, 2009), I did my best to present the problem- a disconnect between what we know about preventing diabetes complications, and the fact that many patients still develop them. In this entry, I want to explore some possible reasons for the “disconnect.”
Using the A1c test as a measure of the degree to which a patient’s diabetes care is being managed optimally
In previous entries, I have discussed the importance of hemoglobin A1c measurements, often called “the A1c test,” in quantifying blood glucose control in people with diabetes. The A1c test is a tremendous advance in diabetes. As recently as the early 1980s, physicians really had no objective way to assess long-term blood glucose levels in patients. Patients could do fingerstick blood glucose testing at home on a regular basis which helped give both patients and physicians some idea of how things were going. But it was not until the A1c test became widely available AND the Diabetes Control and Complications Trial results showed that the A1c test was a powerful risk predictor for diabetes complications that the wheels of progress started moving fast.
We now know that the A1c test is a reasonably reliable measure of a person’s average blood glucose level over the preceding 3-4 months. I say “reasonably,” because the test really quantifies a “moving average,” not strictly speaking, an average over time x to time y. But, even given the test’s limitations as a measure of average blood glucose, it is useful in relating daily patient blood glucose testing to an overall average. But, where the test really shines is as a very reliable predictor for patient risks of developing and showing progression of all diabetes chronic complications. Furthermore, the test is more or less standardized among laboratories in the U.S. and most of the result of the world through a National Institutes of Health supported program called “the NGSP.”. Thus, a simple blood test that requires only a small drop of blood and can be performed in less than 30 minutes can tell a patient and his doctor roughly what the patient’s average blood glucose level has been over the past few months and whether the test result is in a desirable range with respect to risk for the development/progression of diabetes complications. The test has been used not only for routine patient care but also in quality assurance programs. So the point I want to make here is that we now have a tool that lets us quantify how well a patient is doing overall with their diabetes care.
What do A1c test numbers mean?
With respect to interpreting A1c test results, I would consider a level of 4-6% as normal (in my laboratory, the upper limit of normal is actually 5.7%). The American Diabetes Association (ADA) has recommended that patients with diabeetes aim for levels <7% (an A1c of 7% reflects an average blood glucose of about 150-170 mg/dl, with normal about 70-100 mg/dl). The ADA used to recommend that most people with diabetes maintain A1c levels <8% with higher levels requiring “action.” I was disappointed when, several years ago, the ADA abandoned this care goal recommendation. Many patients with diabetes simply cannot achieve A1c levels <7%. It is my opinion that having a single care goal that many people cannot achieve is not the way to help patients achieve care goals. An A1c test result of 7.9% (i.e., <8%) reflects an average blood glucose of about 180-200 mg/dl. Data from the DCCT/EDIC and the UKPDS show that patients’ risks of developing diabetes complications are quite low if the A1c level is maintained at <8% long-term, but not as low in patients whose levels are <7%. Anyway, that’s what the numbers mean. In my discussions I will define “optimal control” as levels <7% and “acceptable control” as levels <8%. But it is important to remember that lower is always better unless the patient is having frequent episodes of hypoglycemia (low blood glucose levels). In fact, a drop in A1c from 10% to 9% decreases risks for complications much more than a drop from 9% to 8%, which in turn decreases risks more than a drop from 8% to 7%. This means that for some patients unable to achieve A1c levels in the desirable range, we as health care givers should be willing to applaud any improvements that the patient makes. This doesn’t mean we (patients and health care givers) should be satisfied with A1c levels that are above desirable levels, but rather, accept that incremental improvements are better than no improvements.
- Why Do Patients With Diabetes Still Develop Chronic Complications?
- U.S. Health Care Reform: Is It Possible to Gain Without Pain?