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Diabetes101:LAB TESTS- Hemoglobin A1c

Posted Jun 05 2009 5:06pm

   Whether you're newly diagnosed or have had Diabetes for years, one test that you should be familiar with and will receive on a regular basis is the Hemoglobin A1c.

   The Canadian Diabetes Association recommends that all Diabetics take an A1c test every three (3) months, and strive for an acceptable A1c of less than 7.0% (less than 6.0% if possible). The Diabetes Control & Complications Trial (DCCT) provides compelling evidence that a 1% reduction in overall A1c values can decrease the risk of Microvascular complications of Diabetes by approximately 30%. Microvascular complications refer to damage of small blood vessels and include kidney diseases, eye diseases and nerve damage.

   The Hemoglobin A1c - formally called the A1c - has a variety of different names, each referring to the same blood test:

    • HbA1c
    • Glycohemoglobin
    • Glycosylated Hemoglobin (Ghb)
    • Glycated Hemoglobin

   Whole blood, or the blood that you see when you cut yourself or have blood drawn, consists of Plasma (55%) and Blood Cells (45%). There are three different types of blood cells: Leukocytes (White Blood Cells); Erythrocytes (Red Blood Cells) and; Platelets (thrombocytes). Leukocytes fight infection and disease with specialized white blood cells while Platelets aid in the clotting processes of the blood. A laboratory Centrifuge is used to separate the plasma and the blood cells by spinning the whole blood until the fluids separate.

   Of all the cells in the body Erythrocytes (pronounced ir-rith-ra-sites) are the most abundant, and they have a life-span of approximately 90-120 days. Erythrocytes are shaped like flying saucers, and they transport Oxygen (O 2 ) from the lungs to the body tissues by binding O 2 to Hemoglobin. Hemoglobin is a protein rich in iron that is carried within RBC's. Erythrocytes are like a train, and the Hemoglobin is the cars on the train that transport O 2 to body tissues in order to keep them alive.

   Glucose circulating in the blood that is not used for energy spontaneously attaches itself to Hemoglobin. This is a normal process called glycosylation, and the binded glucose remains on the Hemoglobin for the lifetime of the RBC. In non-Diabetic individuals, 4.5-6.0% of circulating glucose binds itself to Hemoglobin. Glycosylation is a slow process and, as such, the A1c test is not drastically affected by short-term changes in blood glucose levels.

   Hyperglycemia aggravates glycosylation; the increased blood glucose levels, over lengthy durations, allows glycosylation to occur at an amplified rate. The more unused glucose that is circulating in the blood stream, the more glucose that will bind itself to Hemoglobin. The overload of binded glucose can alter and mutilate cells and structures within the body, leading to Microvascular complications.

   The results of an A1c test show the percentage of glucose that has binded to Hemoglobin, and thus the possibility of any subsequent cell damage. Unfortunately, in terms of blood glucose values, the A1c is only an average and is affected by both Hyperglycemic and Hypoglycemic episodes. In theory, a Diabetic could have an excess of Hypo's, an excess of Hyper's, and a normal A1c value. Frequent blood glucose monitoring and firm BG records are essential in conjunction with A1c tests to decide levels of control, and also any changes in therapy that may be required.

   You and your Physician or Endocrinologist generally decide the frequency of the A1c test, and those with an A1c < 7.0% may decide to have this test every six months. The only commercial, home A1c kit, made by Metrika, is an affordable, single-use test that takes about twenty minutes to complete.

  If you haven't had your A1c done recently (within the past six months), be sure to schedule an appointment with your Physician, or pick up a home A1c kit. Remember, knowledge is power!

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