New System For Reporting Blood Glucose Finalized, A1c Eliminated for Patients

The equation: AG (average glucose in mmol/L) = 1.583 x HbA1c - 2.52, where R2 = 0.836. (Note that 1 mmol/L = 18 mg/dL)

With this system, providers will have three numbers: the usual A1c percentage, the new IFCC version in mmol/L, and the new estimated average glucose.

The implications are that, hopefully, patients will find it easier to integrate this information into their management behaviors and improve control because the average glucose scale matches that of glucose meters.  Also, manufacturers of A1c equipment will need to update their software.  Prior to this new information, the A1c was tied to the results of the DCCT, where a 6% was equal to 135mg/dL.  This came about when they checked the A1c and then looked at a couple of thousand finger sticks and averaged them out.  Now with the use of hundreds of thousands of readings, not just with the finger sticks but also with the use of continuous blood glucose monitors, we have more accurate results.  The equation yields a linear correlation over a wide range of A1c. This means that a 6% is no longer an average of 135mg/dL:  The new numbers:

o 6% = 126 mg/dl
o 7% = 155 mg/dl
o 8% = 182 mg/dl
o 9% = 211 mg/dl
o 10% = 239 mg/dl

Now because of this new equations we have to ask which measure is most important, the A1c or blood glucose? The ADAG trial showed no difference between LifeScan and CGM data. Perhaps A1c is not the gold standard, at least for correlating cardiovascular disease with glucose levels. After all, data presented at EASD showed that patients with the same A1c can have different ‘area under the curve’ PPG. For these patients, high PPG values may be a better indicator of inflammation and CVD risk than A1c.  It should be the combination of data that will most help patients understand how the A1c and the average blood glucose are both important.

Source: Diabetes In Control: Reported at the EASD symposium