Evaluating the Diabetes-Cardiology Interface - Episode 4
Paul Thompson, MD: I want to hit on 1 of the other issues that I’m always trying to talk about, and that is how you can be fooled into not seeing diabetes in borderline patients who have a normal hemoglobin A1C [glycated hemoglobin]. You can be tricked into thinking that there’s nothing going on. Their glucose is a little high. Their hemoglobin A1C is not bad, and you overlook the possibility that they actually have diabetes or prediabetes.
Robert Busch, MD:Hemoglobin A1C is a 3-month average, but the red cells don’t last 3 months if you have hemolytic anemia, certain hemoglobinopathies, and renal disease. In that case, the A1C might not reflect the overall 3-month average glycemic control. There’s a 1-month average we use called a fructosamine. We do that in pregnant diabetics or patients who have turned over a new leaf if they come back to you in a month and you want to show that their average sugar has improved. Those are patients in whom we do a 1-month average. But there are certain patients in whom, if you’re really suspicious that they have diabetes, you do a glucose tolerance test, much like in the old days. The A1C is a nice shortcut, but it doesn’t always reflect whether the patient has diabetes.
Paul Thompson, MD: Bob, is it also possible that the hemoglobin A1C is normal, yet the person has big spikes postprandially that are deleterious? Or does that not happen often?
Robert Busch, MD:Usually, the A1C is pretty sensitive, unless they have some kind of hemoglobinopathy or red cell turnover. If someone had a gastrointestinal bleed or is constantly replenishing with new red cells, that red cell hasn’t been exposed to glucose yet. Your A1C could be better than your glucose levels.
Transcript Edited for Clarity