The A1C : “Say Hello To My Little Friend…”

Glycosylated Hemoglobin

Called also hemoglobin A_1c.

Hemoglobin A with a glucose moiety attached to the amino terminal valine of the beta chain. This type of hemoglobin is made at a slow constant rate during the life span of the erythrocyte.

Increased levels correlate with glucose intolerance in diabetes.

With adequate insulin treatment, levels return to the normal range and periodic assays can be helpful in evaluating effective control of diabetes mellitus.

Editor’s Note:

I do all of our STS data harvesting and chart abstraction.  I used to hate it with a passion- as “busy work” until I assumed some responsibility at our institution in terms of improving outcomes, and accurately mining our data.

Well, after 3 years of doing it, and paying attention to our outcomes, and learning to RESPECT the long road patients endure AFTER cardiac surgery, my perception changed and became a little less myopic.

So on to a subtle- but intriguing lab value in our preoperative workup- that most of us see, and more or less set aside in deference to the much more recognizable serum glucose that always finds it’s way into our perfusion records…

Say hello To My Little Friend…

The A1C

HbA1C

Lab Values

“For people without diabetes, the normal range for the hemoglobin A1c test is between 4% and 5.6%. Hemoglobin A1c levels between 5.7% and 6.4% indicate increased risk of diabetes, and levels of 6.5% or higher indicate diabetes.”

Translation:  > 6.5 = BAD

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STS

Glycosylated hemoglobin, HbA1c, is a form of hemoglobin used primarily to identify the average plasma glucose concentration over prolonged periods of time. It is formed in a non-enzymatic glycation pathway by hemoglobin’s exposure to plasma glucose. Normal levels of glucose produce a normal amount of glycosylated hemoglobin. As the average amount of plasma glucose increases, the fraction of glycosylated hemoglobin increases in a predictable way. This serves as a marker for average blood glucose levels over the previous months prior to the measurement.

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As A Predictor for Afib (post CPB)

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Conclusions: Preoperative hemoglobin A1c independently predicts the occurrence of AF after isolated off-pump coronary bypass grafting.

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As a Factor for Reduced Sensitivity to Insulin

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Conclusions: In diabetic patients, HbA_1c levels predict insulin sensitivity during surgery and possibly outcome. Intraoperative insulin resistance is associated with an increased risk of complications, independent of the patient’s diabetic state.

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As a Marker for Long Term Survival

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Using a marker of glucose control such as a preoperative HbA1c may provide more accurate risk stratification to predict long-term outcomes of patients with diabetes mellitus.