HbA1C, and deviation from average BG

[david.bligh]

I'm due to go for a new HbA1C soon, and Im wondering... Whilst my meter says that the average BG is 5.9mmol, the range goes from 1.6 to 12.4. Will the average BG to HbA1C calculator still give me a decent idea of what it should (hopefully) be?

 

[jopar]

I really don't know as I don't use on line converters..

Whether a meter tally's up with an HbA1c will be totally dependant on two factors, how many times you test on average a day, and what happens to your blood glucose between testing..

What is your standard deviation saying?

What I actually do, is I only ever use one meter for all testing (keeping my back meter for emergency use) I then note down what my meter tells me is my average is for 90 days then when I get my HbA1c result compare the differences in that meter, if you've got a good monitoring regime, then you can work out and know what to expect.. One my pump meter now I know to expect my HbA1c to come in 0.4 below what my meter is telling me..

But with saying all that, I don't sort of take much notice of my HbA1c as such, but work with my meter and looking at the SD both overall and for individual meals aiming to keep this to a minimum as the lower the SD over all and meal to meal the better daily control you have, and the better HbA1c result you get..

 

[david.bligh]

I havent uploaded my results in a while to CareLink, so I cant see my SD. Generally however, they're normally between 3-7, with the occasional high up to 12. I'd say this only happens maybe once a week?

BG before meals ~ 5
BG 2hrs after meals ~ 8
BG spot checks ~ 3-7

My HbA1C results are really important to me. I have always had results greater than 12% until my most recent test (2 months after the pump) which was 8.3%. I am hopeful to get it under 6% in my next test.

**Aware that I'm using the %-ages and not the new mmol system. Prefer it that way!!**

 

[AMBrennan]

Here's a calculator.

However, your meter average is (probably) not a very good predictor for your HbA1c because all measurements carry equal weight which is clearly not realistic - e.g. BG will be low all night (12h+) but the corresponding measurements (morning fasting BG) only accounts for 1/6 of the average.
That assumes the standard 6x tests per day; if you just test in fasting BG (which is what I do) in the morning and post-meal BG then the unweighed average will be even more biased; if you follow the recommendation of others and only test pre-meal then the average will still be biased.

Edit to add: At the end of the day, I think that morning fasting readings will be a much better indicator (assuming post-meal spikes are "small") than a simple average that is biased towards unusual observations. I wonder if there is statistical data to test that hypothesis?

 

[jopar]

Dave

I know that you say the HbA1c is important to you, and I didn't meant don't pay any attention to them, but if you'll working on the day to day control the HbA1c will look after itself..

 

[david.bligh]

I think HbA1C is just a nice way of giving yourself an aim, and a way of giving yourself a pat on the back if you've done good. :clap:

Each to their own though.

 

[noblehead]

David,

Without constantly testing the meter averages are meaningless and the hba1c is a far better indicator of overall control, but those like us using insulin who can test up to 8-10 times a day the meter averages are a good indicator of what our hb's will be like.

On the last 2 occasions I've had my results my meter has been .2 and .3 out so they won't far away.

Nigel

 

[david.bligh]

Thanks Nigel! I think it would be interesting to get an idea of what other peoples HbA1C results are like. *starts new topic!*

 

[leggott]

just like you I like to get a good HBA1c for my kids and it's what I call my 'good mummy award' and my pat on the back! But, I do agree with both Jopar and Noblehead. My children will always get HBA1cs that are within .1 or .2 of each other, yet I would say that my son's control is far more erratic than my daughters! I agree that if you do a lot of tests a day, then the meter does give a very good indication of your HBA1c.

 

[david.bligh]

I think my big hang up on believing this is that I've never had a good %age. Always been in the teens until recently when I got 8.3%. My meter now looks like my next one should be 5.?%. To good to be true! Will let all know when I've had it done anyway!!

 

[leggott]

It really all depends on when you test with your meter. I would expect to see lower readings from my children at 4 hours after eating than at the 1 - 2 hour point. Therefore if the majority of tests I do are done after 4 hours then the average would be lower if that makes sense!

That's a fantastic reduction to have achieved so let's hope your meter average on this occasion does give a good indication of your next HBA1c.

 

[david.bligh]

Quick one to anyone who is interested... Will dropping my HbA1C quickly have an impact on my eye health? I have been diagnosed with background retinopathy and have recently had a peripheral vision test (results on 1st Dec).

 

[daisy1]

It could do. Better not to go down too fast.

 

[ebony321]

Quick one to anyone who is interested... Will dropping my HbA1C quickly have an impact on my eye health? I have been diagnosed with background retinopathy and have recently had a peripheral vision test (results on 1st Dec).

It can be that way if you drop your HBA1c quite dramatically. It's always best to do it slowly to ensure you keep your peepers nice and healthy

My screening tests show small changes in my eyes due to my diabetes, not anything major that needs treatment, my eyes are still good (reading glasses only) but i DID bring my hba1c down dramatically on several occasions. In just over a year i've gone from 16.1% to 6.6% some jumps were bigger than others. One being from 12.1% to 8.4% in six weeks. That as the result of the DAFNE course and starting to carb count which was obviously going to improve my control quite dramatically.

 

[noblehead]

Quick one to anyone who is interested... Will dropping my HbA1C quickly have an impact on my eye health? I have been diagnosed with background retinopathy and have recently had a peripheral vision test (results on 1st Dec).

Yes it can as the eyes are susceptible to change and that is why they say lower it gently over a period of time.

This site offers some great advice on this subject:

http://medweb.bham.ac.uk/easdec/

Nigel

 

[SugarPlums]

HbA1C is a non-standardised test which varies from one hospital to another, if you find a way to relate it to average BG readings please tell us.

 

[phoenix]

Laboratory HbA1c testing is standardised within the UK and has been for a fairly long time. Until recently results were aligned to tthe method used in DCCT.
Results were not necessarily comparable internationally and one or 2 countries such as Japan developed different technologies and their HbA1cs were calibrated differently.
Improved technology and international improvements in testing capabilities have lead to changes in calibration recently and greater international co-operation and standardisation, that's part of the reason for changing units on the HbA1c.

http://www.diabetes.org.uk/Guide-to-dia ... essionals/
or if you want very full details
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1240025/

The international working group also spent time researching whether the average HbA1c actually corresponds to the average blood glucose (using continuous monitors) . For most but not all people it's a good correlation .
There is a formula for finding the average glucose from the HbA1c and that's what calculators like this one are based on.
http://professional.diabetes.org/GlucoseCalculator.aspx
How well they work the other way round (average readings to HbA1c) will depend on the amount of reading s and when they were taken. The links at the bottom are to some of the research on this.