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A1C Testing


What is A1c?

A1c (sometimes referred to as Glycated Hemoglobin A1c, or HbA1c) is a measure of the average blood glucosemeasuring A1c in type 1 diabetes over the past three months. It suggests how well blood glucose has been controlled during that time.


How Does A1c Measure Average Blood Glucose?

A red blood cell lives for about three months. During that time, hemoglobin (a part of red blood cells) picks up sugar from the blood. If blood glucose is often high, more sugar will stick to the hemoglobin, resulting in a high A1c.


How is an A1c Test Performed?

A blood sample can be taken from the fingertip or from a vein in the arm. If in doubt, ask your child’s diabetes team what kind of sample is needed and where to go to have it done. If the most appropriate method is to have a blood sample taken from a vein, you may choose to use a topical anesthetic (such as EMLA™ cream, Ametop Gel™, or Maxilene 4™) to numb the skin. Maxilene 4™ is more minimally vasoactive than EMLA™ which means that it is less likely to cause the vein to shrink and therefore might make it easier for the lab technician to find the vein.

tips from the trenches of type 1 diabetes
I have preferred different approaches at different times in my son’s life: when he was very little, I was uncomfortable with the thought of obtaining a blood sample via a needle in his arm –he was so little, and I felt like he got enough needles as it is, so I wanted to spare him this one by opting for a finger-prick to obtain a sample. For a time, that was the right decision for our family. Lately, we have opted for obtaining a blood sample from a vein in his arm, and have found that method more efficient, without much more reaction from my son. Currently that is the right decision for our family – but every family is different. Also, for a venous blood sample, we have used EMLA cream at times and we have gone without it at times, and have found that it may actually make it harder for the technician to locate a vein efficiently, so currently we do not use EMLA at blood test time.  ~Michelle

tips from the trenches of type 1 diabetes
I too have preferred different approaches over the years for my son. When he was very little, we always used EMLA but chose to get his blood work done at the Children's Hospital where they were experts at dealing with "little" veins. It was easier for them to find the vein if I had my son drink lots of fluids about 1 hour prior to the test. When he grew bigger, we still used EMLA but we were able to use the local lab as long as he drank a lot prior to the blood test. We then transitioned to not numbing the skin, still drinking lots and a small reward after. This method was used for years, with my son greatly looking forward to the "reward" after the blood test and thus not dreading the actual test so much. ~Danielle
  

In many cases, the choice of method is yours. But here are some additional things to consider:
  • The finger-poke is not necessarily less painful – the lancet used is bigger than the one your child uses to check blood glucose daily, as a larger sample is needed to arrive at an accurate A1c. Also, the finger often has to be squeezed quite firmly to obtain an adequate sample.
  • Not every lab has the materials in stock that are needed to do a finger-poke A1c test (although we have had pretty good luck with the lab at the Alberta Children’s Hospital).
  • Drawing blood from a vein is more efficient, so the overall fear-factor may actually be reduced by using this method.
  • If other blood tests are needed (such as a thyroid test), a blood sample will need to be drawn from a vein anyway, so you may just opt to have both tests done from that sample.
  • If a lab to meter comparison is needed, a blood sample will need to be drawn from the vein, as a very large amount of blood is required and it is very challenging to obtain this much from a finger-poke. However, you (the parent) may provide the lab-to-meter-comparison sample (rather than your child), if you prefer, and then (in a separate sample) your child only has to provide the finger-poke sample for the A1c test.

tips from the trenches of type 1 diabetes
In the end, no matter the method, drawing blood for lab blood work is, for me, still one of the hardest parts of parenting a child with diabetes. It’s real challenge for me emotionally, even though my son copes quite well and shows little reaction or pain. So in terms of the division of responsibility that my husband and I have worked out, taking our son for blood work falls on his list. (Although if that is not feasible for a given visit, I will do what needs to be done.) For your family, consider who would be the best choice to accompany your child for blood tests. Who is more comfortable with the process of drawing blood, and would therefore provide a calm model for your child? If neither spouse is comfortable with this task, or if you are a single parent and find this process very difficult, consider asking a close family member or friend to accompany you and your child for support. If this process causes extreme distress for your child, you may consider contacting a psychologist or behaviourist for strategies to reduce this distress.  ~Michelle

 

How Often Is This Test Done?

The A1c test is usually done every three months.



What Should the A1c Result Be?

The normal range (for persons who do not have diabetes) at an Alberta Health Services lab is 4.3-6.1 %. This range may vary between labs. Most people with type 1 diabetes do not have a “normal” A1c level.  Speak with your diabetes team about your child’s target A1c.

Research shows that lower A1c levels can greatly decrease the risk of long term complications (such as nerve, kidney and eye damage)1. In fact, estimates are that even a 0.5% reduction in A1c results in a significantly lower risk of future complications. If your child has a high A1c, you and your child’s diabetes team will develop an action plan to help lower it. On the other hand, it is important to keep in mind that efforts to lower your child’s A1c must be balanced with safety (in terms of low blood glucose). This is particularly important for younger children and/or those who are not aware when they are experiencing a low.

The International Society for Pediatric and Adolescent Diabetes (ISPAD) recommends a target HbA1c of less than 7.5% for all age-groups of children and teens.2

The Canadian Diabetes Association Clinical Practice Guidelines3 break down the recommendations according to age, suggesting the following general guidelines for targets for glycemic control for children and adolescents:

Age
(years)
A1c
(%)
Fasting/
preprandial

BG
(mmol/L) 
2-hour
postprandial

BG
(mmol/L)
Considerations

 
<6 <8.0 
6.0 – 10.0
Extra caution is required to minimize hypoglycemia. 
Consider target of < or = 8.5 if excessive hypoglycemia occurs.

6-12
7.5 
4.0 – 10.0  -

Targets should be graduated to the child’s age.
Consider target of < or = 8.0 if excessive hypoglycemia occurs.
 
13-18  ≤7.0  4.0 – 7.0  5.0 – 10.0 
Appropriate for most adolescents.
In adolescents in whom it can be safely achieved, consider aiming toward normal post-meal range (i.e. A1C ≤ 6.0%, fasting/preprandial PG 4.0-6.0 mmol/L and 2-hour postprandial PG 5.0-8.0 mmol/L)




How Does A1c Relate to Average Blood Glucose?


The A1c number (expressed as a percentage) reflects the average blood glucose over the previous three months as follows:


A1c Conversion Chart4

A1c value


Average
Blood Glucose

(mmol/L)


5.0 %

5.4


6.0 %
 
7.0
 

7.0 %
 
8.6
 

8.0 %
 
10.2
 

9.0 %
 
11.8
 

10.0 %
 
13.4
 

11.0 %
 
14.9
 

12.0 %
 
16.5
 

13.0 %
 
18.1
 

14.0 %
 
19.7
 


For example, if the result of your child’s A1c test was 7.0% (the CDA-recommended upper limit for A1c for 13-18 year olds), his average blood glucose over the past 3 months was approximately 8.6. If the result of your child’s A1c test was 13.0% (a result higher than the CDA-recommended upper limit for any age group), his average blood glucose over the past 3 months was approximately 18.1.

If your child’s latest A1c result does not appear in the above table, an estimate may be calculated via the following formula:

[A1c (%) x 1.59] – 2.59 = average Blood Glucose (in mmol/L)

For example, an A1c result of 8.4 represents an average blood glucose of [(8.4)x1.59]-2.59 = 10.8 mmol/L.



The Significance of A1c Results

The “take home” lesson about A1c testing is that lower is better (within the boundaries of safety regarding hypoglycemia). However, it is important to interpret A1c within the appropriate context.

First, it’s important to note that the A1c value is an average, and as such, does not take into account the range of blood glucose readings which contributed to a given result. That is, returning to the example above, an A1c of 7.0% suggests an average blood glucose of 8.6 (from the A1c Conversion Chart above). This value may be obtained by spending all of the time right at 8.6 (highly improbable in real-life, but theoretically useful for this example); it may also be obtained by spending half of the time at 2.6 (in a hypoglycemic state), and half of the time at 14.6 (in a hyperglycemic state). Therefore, to get a more complete picture of how well-controlled blood glucose is, we need to also consider other data measures, such as the maximum and minimum blood glucose readings, the percentage of readings which fall in the target blood glucose range, and the frequency of low blood glucose readings.

Further, if your child’s A1c is already within the recommended range and everyone is busting their butts to lower it another tenth of a point, you may want to consider whether the cost of achieving this goal is worth the benefit of a very-slightly-lower A1c. Our constant efforts to achieve lower and lower A1c’s may communicate to our kids that, no matter how hard they work and no matter how good it is, it will never be good enough. If this is the message your child is getting, it may be worthwhile to add their emotional health into the cost-benefit equation.

Finally, just as with the results of blood glucose (finger stick) checks, it’s helpful to talk about A1c results as being “above”, “within” or “below” recommended levels, as opposed to being “bad” or “good”. Every A1c result is a valuable result, as it gives us information about how we may (or may not) need to change our behaviour.

tips from the trenches of type 1 diabetes
When is a test not a test?
When I cheered out loud for a lower-than-last-time A1c result, I had the endocrinologist ask me, “You realize it’s not a test, don’t you?” But to me, it had always felt like a test: Did I “pass” as a parent? Was I doing enough for my son’s glycemic control? Although it’s tempting to personalize the result, it’s important to remember that the A1c test is a test of your child’s blood; it is not a test of you as a parent, nor of your child as a person. What it is, however, is valuable information to guide your/your child’s ongoing decisions and goals about his diabetes care. Further, if the result is high, this may indicate that you (and your child, as age-appropriate) have important work to do to improve blood glucose control. If the result is significantly lower than recommended, that may be a sign that he is having undetected lows. Either way, it’s a good idea to talk with your diabetes health team about the result and whether any changes should be made.  ~Michelle


(For more information on what data numbers to look at and how to make sense of these numbers, see BG Management/Data Analysis.)



1The Diabetes Control and Complications Trial Research Group. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. N Engl J Med. 1993 Sep 30;329(14):977-86.

2Rewers M, Pihoker C, et al. Assessment and monitoring of glycemic control in children and adolescents with diabetes. Pediatric Diabetes, 2009;10 (suppl. 12): 71–81.

D. Wherrett et al. Canadian Diabetes Association 2013 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada: Type 1 Diabetes in Children and Adolescents. Can J Diabetes 37 (2013) S154.

4http://www.bcchildrens.ca/NR/rdonlyres/27E87F65-7959-4396-8B52-14E6A5BCB42D/30101/a1cglucose.pdf



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The above information was significantly modified with permission from The Alberta Children’s Hospital Diabetes Clinic information handouts.

The above information was reviewed for content accuracy by clinical staff of the Alberta Children’s Hospital Diabetes Clinic.

This material has been developed from sources that we believe are accurate, however, as the field of medicine (in particular as it applies to diabetes) is rapidly evolving, the information should not be relied upon, as it is designed for informational purposes only. It should not be used in place of medical advice, instruction and/or treatment. If you have specific questions, please consult your doctor or appropriate health care professional.


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