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Question:

From Iran:

My three year old nephew's first A1c, three months after diagnosis, was 7.8. The laboratory that conducted the test says their normal range is 4.4 to 6.7. The ADA says an A1c should be less than 1% above the upper limit of normal for the laboratory performing the test. It seems somehow not tight enough or kind of conservative if you prevent hypoglycemic reactions.

During this three first months of diabetes and tears and sighs, we had about three or four readings (caught early) under 50 mg/dl [2.8 mmol/L]. One was 20-something mg/dl [1.1 to 1.6 mmol/L] and we administered glucagon. My nephew was alert though and speaking. We were told that the glucagon had not been necessary. It's very unlikely that we have had any lows at night since we were monitoring him around the clock in shifts. We also had a 500+ mg/dl [over 27.8 mmol/L] reading, a couple 400+ mg/dl [over 22.2 mmol/L] readings, three to five 300+ mg/dl [over 16.7 mmol/L] readings, and five to ten 250+ mg/dl [over 13.9 mmol/L] readings during this three month period. At the hospital, during the first three days, I guess we were somewhere around 300 mg/dl [16.7 mmol/L] to 500 mg/dl [27.8 mmol/L]. It's their policy. The nurses choose the easier alternative here and nonchalantly trade long-term damages for hypoglycemia because it's easier to keep the child in 400s mg/dl [over 22.2 mmol/L] and cause future complications than keeping him in 200s mg/dl [over 11.1 mmol/L] and be blamed for a possible low.

I'd like to have your opinion on this first A1c of ours. I do know a lot about A1cs though and that it's the "quality" of the A1c that matters (less variability and smaller standard deviation) not the number. I also know that lows will kind of compensate for highs. But, I also know that there is a lot more you can tell me.

Answer:

Glycosylated (or glycated) hemoglobin values are measurements of how much glucose is "sticking" to hemoglobin. A common tool to measure the glycosylated hemoglobin is the hemoglobin A1c (A1c) test. The amount (percentage) of glucose that adheres to hemoglobin depends, in part, to the amount of available glucose and, in part, to the amount and quality of the available hemoglobin. Hemoglobin is located within the red blood cells. The average "life span" of a red blood cell is about 120 days.

So, measurement of the A1c is better a measurement of overall glucose control over the prior several weeks: 120 days ago, your nephew made new red blood cells with hemoglobin in it and some glucose then stuck to it. That glucose does not "unadhere" until the red blood cell is at the end of its days, about 120 days later. So, on any given day when the A1c is measured, there are new red blood cells, young red blood cells, middle aged red blood cells, and old red blood cells.

You indicate that your nephew has been treated for diabetes three months (90 days) ago. The A1c is now 7.8%. It would be nice to know the value at the time of diagnosis so that you can see the (presumed) improvement as his glucose overall has improved and wether he has recycled out much of the older red blood cells from 90 days ago.

There are no completely agreed upon criteria for targeted A1c values in children, especially younger children: one must balance out the benefit of good glucose control with the risk of elevated glucose but also the risk of hypoglycemia. A 7.8% three months into diagnosis, knowing that some of those red blood cells are flush with glucose from four months ago, strikes me as a very good value.

The A1c is to help you perceive the forest-from-the-trees: the glucose levels that you check at any given time are to help you gauge insulin dosing, meals, activity planning, use of extra glucose or glucagon, checking for ketones, etc. at THAT moment. The A1c gives you knowledge of overall glucose control, including those other 1430 minutes of the day when you not checking.

As an aside, I agree that the use of glucagon as you described was probably not required. It is typically required for low glucose associated with convulsions or loss of consciousness.

You should have on going discussions with the child's diabetes specialist.

DS

[Editor's comment: The gradual reduction of blood sugars at diagnosis is related to trying to prevent the development of cerebral edema, usually in the presence of ketoacidosis, which is more common at diagnosis. BH]

DTQ-20061105173818
Original posting 2 Dec 2006
Posted to A1c, Glycohemoglobin, HgbA1c

  
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Last Updated: Tuesday April 06, 2010 15:10:10
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