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What is the correct measuring principle for BG these days?

O

Omnipod

Well-Known Member
Messages
533
Location
West Sussex
Type of diabetes
Type 1
Treatment type
Insulin
Is it a1c or is it GMI?

I have changed from MDI to a CGM and closed loop pump.

My report for 3 months shows a drastic improvement in my blood glucose.

My Time in range is 70%. My average BG has dropped from 12.3mmol to 10.6 mmol.

My GMI has dropped from 8.6% to 7.9%.

If I convert from GMI to A1C, (A1C=(GMI+2.59)/1.59) 7.9 + 2.59 / 1.59 = 6.5%

I just had my a1c blood test and the result is 8.2%.

I just do not know what the measuring principle is anymore. Some say the Dexcom readings are more accurate.

Any information please.
 
Omnipod said:
I just had my a1c blood test and the result is 8.2%.
Click to expand...
Well if you use the convertor here (https://www.diabetes.co.uk/hba1c-units-converter.html), it does show that 8.2% (66.1 mmol/mol) does equal an average of about 10.5 mmol/l, which goes with the average you stated you were now down to

Note, I have no idea what GMI is- though a quick google search found this (https://diatribe.org/diabetes-technology/using-gmi-estimate-your-a1c-how-accurate-it) note this is just the first one I looked at , they may all say different things for all I know
ie your gmi of 7.9 is pretty close to 8.2%, not sure what calculation you are using - maybe like with blood glucose readings there is a UK measurement system (mmol/l) and a US version (mg/dl) - which uses a different calculation
 
Hi - HbA1c has been in use for a while but was only formally adopted as the measure in 2010. Historically HbA1c was reported as a percentage - being the percentage of a particular haemoglobin protein that had become glycated - had had a glucose molecule attached to it. Most of the world now uses (according to Bilous and Donnelly, anyway) the IFCC mmol/mol, although it's clear this is not widely used in the USA and many UK doctors still quote HbA1c in percentages.

As it doesn't test blood glucose directly, HbA1c is a proxy measure that allows an estimate of the likely blood glucose levels over the past 3-4 months. It isn't perfect by any means and its limitations are well known.

Conveniently the DCCT %s align neatly with mmol/mol - 5.5% is 38, 6.0% is 42, 6.5% is 48mmol/mol which makes me ask questions about how and why some of the mmol/mol figures were selected for diagnostic purposes.

I had not heard of GMI before and the Handbook of Diabetes doesn't reference it at all. I can see why Dexcom are pushing it - it's essentially an advert for their product. I'm not convinced by the "no lab interference" argument at all.

GMI seems to be a calculated derivative of CGM measurements - which don't directly test blood glucose either. If the reported results above are accurate, it means (assuming in IFCC terms that 1% DCCT is roughly equal to 11mmol/mol) that nearly three quarters of the GMI results differ from HbA1c by a considerable amount - enough in over 20% of people to have you diagnosed as T2 when your BG is actually normal according to HbA1c, or vice versa.
 
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