# RE: [IP] mg/dl vs mmol

```Darrin Parker [mailto:email @ redacted] wrote:

> A1C results in no way reflect average bg's in any
> measurement!  A1C's are
> good only as a measure of improved or the opposite of control of an
> individual.  With enough stats one can get an "average bg"
> equivalent to
> the A1C result but this is very individual!  We cannot
> compare A1C's among
> us!

Au contraire, mon ami!

HbA1c most certainly *IS* an average BG reading.  Of course, there are many
ways to calculate an average.  It is not an arithmetic mean, but the result
of a biological process that is far more complicated.  But it also
translates pretty accurately to an arithmetic average of home BG tests.
Where it fails as an average is that there is an inherent assumption in an
arithmetic average that the process is linear (i.e. there is a one to one
association with one value to another).  Still, it is valuable for a lot of
people as a translation to their own testing.

But with regard to your second statement about being good "only as a measure
of improved . . .", HbA1c is the *principal* measure of control, and it is
our personal BG tests that are the approximations used to detect trends,
etc.  The measurement used in the DCCT (and, I think the UKPDS) is the
HbA1c, not fasting glucose or any other point estimate of blood glucose
(which is what our meters give).

You are correct in a sense that HbA1c should not be compared in that each of
us has levels of control that we can attain.  While one person may be very
frustrated with a post-meal test of 160, another might be ecstatic when he
or she can get it below 200!

There are several methodologies for testing HbA1c, and that is where one
needs to be cautious about comparing results.  Some that are done in
physicians' offices are, more often than not, waived tests (see my comment
about waived in my post about the GlucoWatch).  These have the same accuracy
and precision requirements as our personal meters (approx. +/- 20%).  Tests
done in most clinical labs will be moderate tests, but some have better
accuracy and precision than others.  The only time one can really compare
results is if one knows that the equipment and methodology are the same for
the samples being tested.  FWIW, the "gold standard" for HbA1c testing is
column hemochromatography, a high complexity test requiring special training
of the lab technician doing the test.

Jim Handsfield
email @ redacted OR
email @ redacted

The opinions expressed are mine and may not represent those of my wife who
runs our house and makes more important decisions than I do.
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