It has been known since the 1970s that glucose (sugar) can attach to proteins in the blood. If the sugar in the blood is high enough for long enough then the attachment of the sugar to the protein becomes permanent.
The demonstration that the development of microscopic complications in patients with type I diabetes can be slowed by treating high sugars led to the pursuit of measuring blood glucose levels, thus the development of the A1c test. In other words, when high sugars in type 1 diabetics were treated it reduced complications from developing and thus the need for the A1c test to measure.
The most useful test for measuring this phenomenon is called glycosolated hemoglobin, or the HbA1c. Red blood cells readily attach sugar molecules. Just as in the above scenario, the amount of sugar and the permanency of the bond is proportionate to the amount of sugar present in the blood. Since red blood cells only survive 120 days in the blood, the A1c is a measure of the average blood glucose over that 120 day time frame.
There are now many studies and plenty of data supporting the correlation of the A1c to diabetes control. In fact, the measure of A1c is now the means by which to diagnose new onset diabetes.
There are, however, sources of potential error related to the A1c values. This test is influenced by red blood cell survival. If a person has iron deficiency anemia or B-12 or folic acid deficiency the result of the A1c may be falsely high.
If there is a hemolytic anemia( blood loss) causing the marrow to produce young blood cells the A1c value may be falsely low.
If there is a hemoglobin problem such as sickle cell disease or thalassemia the values may also be off( high). Other problems such as a chronic disease state such as kidney disease may also give false values. Other issues that affect the A1c test includes: if you are on dialysis, taking erythropoietin or possibly of Black or Hispanic descent.
If the scenario exists where the A1c values are high but the blood glucose levels are excellent, I advise checking the before meals sugar as well as two hour after meals sugar and adjust medications appropriately.
Let’s consider the issue of high blood glucose values after meals for a moment. Optimal treatment includes changes in either nutrition or insulin regimen. For example, a large meal containing a lot of quickly absorbed carbs and low in fiber may cause a large post meal hyperglycemia. Changing the meal, eating less with each meal, eating more in between meals, increasing the amount of soluble fibers should lower post-prandial sugar level. Otherwise, using more premeal insulin of the short acting variety may be of benefit.
The level of A1c to help prevent complications for type 11 diabetes is clear: 7 %. This is based upon a large study called The United Kingdom Prospective Diabetes Study. For older patients is especial, care must be taken to avoid low( hypo) sugar reactions! That being said, it is very clear sugar values are directly related to future complications i.e. a one percent fall in A1c was associated with a 35% reduction in microvascular disease.
So, follow up with your doctor to check your A1c level every 3 months if you are diabetic!
http://www.medindia.net/patients/calculators/bloodsugar-HbA1c-convertor.asp
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