Things are about to change in many ways for both patients and the clinicians who help these people to manage their diabetes. One notion that I’d like to state is that there are two kinds of A1c; the Physician’s A1c and the Patient’s (and in some cases the patient caregiver’s) A1c.

In the present day, the A1c is a routine blood test scheduled to coincide with the quarterly physician visit. The data from this test is sometimes available at the visit but for most people it’s a lab that comes after the visit. Regardless, appointments are not dependent on having a current A1c. Based on the A1c, the physician may increase or reduce meds, introduce insulin or sensitizers, etc… but none of those decisions have much to do with A1c variance between tests unless the results exceed some critical and arbitrary threshold.

For example, there is no hard and fast guideline for what to do when a patient goes from and A1c of 8.1 to an A1c of 7.2 (3 months later). As has been said quite often, blood sugar control is an art form not a science.

Due to several factors, the role of A1c as a somewhat arbitrary generalized retrospective on control is morphing into a very important diagnostic tool that needs to be used by the patient for behavioral feedback. After all, diabetes is all about behavior whether you’re type 1 or type 2. Almost nobody checks their blood sugar around the clock either so even the most frequent blood sugar checkers are only able to see glucose variability (swings) over 50% of the day.

Assumes 4 blood sugar checks per day with each check offering insight into the preceding 30 minutes and the subsequent hour on average. That means each check accounts for 1.5 hours times 4 checks per day and that equates to roughly 6 hours out of every 24. Even if we double it that gives us 12 hours of insight. Hardly enough to adequately control blood sugars using artificial methods like carb estimating, activity guessing and meter based blood sugar level approximations (meters are roughly 10% to 20% of - plus or minus).

Enter: the new continuous glucose monitoring system technologies.

The promise is 24 x 7 x 365 insight into the world of Diabetes Cause and Effect. Talk about an educational tool for helping patients to measure, understand and act! However, when using one of these devices, it is critical that the patient calibrate the continuous data with meter data. So, we now have 24 x 7 insight but with the caveat of the data only being within +/- 20% of the meter and the meter only being within +/- 20% of the 15 minute old actual blood sugar level.

Continuous Monitoring is for real-time trend-based management - not a precision Swiss time piece for keeping the railroad on schedule.

One of the natural tendencies of being on a cgms is to use your meter less over time based on trust regardless of what the indications say about always using a meter test before dosing insulin or taking some other critical action.

So let’s forget the math for a minute and realize that there is huge potential for the patient to end up in the weeds and when they get their quarterly A1c at the physician’s office or lab…drum roll… the patient is surprised and the physician is unphased. After all, the A1c tells no lies, right and it is what it is. There’s a physician-patient moment I don’t need to be in on.

The physician performs his/her art and counsels the patient… but not much to say beyond what the patient already knows. There are obvious exceptions to this but that’s how most encounters go especially with the kind of patient who would be willing to use a cgms.

For the patient however, the A1c is actually the only data point you can trust. The savvy patient will take the average from their cgms and compare to the translated A1c blood sugar average as a quick sanity check. What does it mean when these two numbers disagree?

Herein lies the new role of the A1c in the management of diabetes. Other than 15g of carb to treat a low, the A1c is the only number you can trust if your goal is to stave off long-term complications. It is the ultimate form of calibration for the cgms and this new role dictates several new ways to use the A1c. It also means that the A1c should be performed more frequently and anything more than a +/- 0.1 variance from the True A1c is unacceptable.

With this in mind, the Patient’s A1c becomes the primary guiding light for the patient while the Physician’s A1c is that data point used to manage patients within a practice; two very different goals with two very different sets of requirements and different use cases for utilization of the A1c in the management of diabetes.

Maybe we users of cgms should start referring to the A1c as the Master Calibrator?

Every day brings us closer to a new way of communicating average blood sugar levels with patients. Thanks to work going on in Europe, a research team is collecting new data with the help of continuous glucose monitoring systems and comparing that data to people with type 1 and type 2 diabetes to come up with a new formula for the conversion. The research is not yet finished but I was able to glean new insight thanks to an article over at Diabetes Health:

“Using the previous nomenclature, the ADA had recommended that people with diabetes aim for an A1c of less than 7% and ideally below 6%. As best we can tell, it appears that using the new standards, a 7% A1c would be the equivalent of 155 mg/dl, and a value of 6% would be the equivalent of an average blood glucose value of 126 mg/dl.”

Keep in mind that the current translation of A1c to average blood glucose levels uses a formula derived during the landmark DCCT which I’ve blogged on previously.

The old way (the one that comes from a study that was already paid for and required no new research dollars and that we already use to report A1c and MBG to patients in our HomeCheck programs) indicates that a 6% A1c is equivalent to an average of 135 mg/dL while an A1c of 7% is equivalent to an average of 170 mg/dL. Here’s the ‘old’ conversion formula for figuring A1c to Mean Blood Glucose (MBG):

(% A1c x 35.6 - 77.3) = MBG mg/dl ( r ) of 0.82

REFERENCES: DCCT GROUP, NEW ENGL. J. MED: 329, 977-986 (1993) SANTIAGO, J.V., DIABETES, 42, 1549
1549-1554 (1993) DIABETES 1997; 46 (SUPPL 1): 8A, DIABETES CARE 1999; 22 (Suppl. 1): S32-41

If the new conversion formula holds, the mean difference we’re talking about here is calculated ‘thusly’:

[(135 - 126) + (170 - 155) / 2] / [(135 + 170)/2] = 12 / 152.5 = 7.9%

I’m not sure that the new formula vs the old formula matters that much. My point is, thanks to the newly funded research using the state of the art technology, we can be reassured that there is a direct correlation between A1c and average blood glucose levels as measured by electrochemical sensors (meters and cgms). I suppose there is a good argument for doing this even if it seems somewhat redundant.

The focus of this research and the forthcoming emphasis on ADAG vs. A1c (which will simply be an input to the formula) needs to be a realization that blood sugars in the currently acceptable targets of 7% A1c and its correlated ADAG of 155 mg/dL are completely unacceptable except in certain conditions of co-morbid conditions and/or to avoid severe hypoglycemia in some patients.

While the debate will rage for years whether or not it is beneficial to patients to use average blood sugar as represented by mg/dL vs. A1c we can only hope that the new research will publish final results ASAP and we can then get on to the business of communicating to patients why they should be striving for near normal (non-diabetic) glucose levels and why they should be demanding improved accuracy and precision from the diagnostic tests used to determine the true A1c, MBG and ADAG. Without an accurate A1c, the formula doesn’t matter or otherwise GIGO (garbage in garbage out).

ADAG or no ADAG, teaching patients advanced self-care skills via cause and effect via aggressive management programs is the key to a long and healthy life and that includes frequent checks on current blood glucose levels to avoid severe hypoglycemia and frequent A1c checks to determine recent average blood sugars.

Here it is! Making great progress on this front lately and thought I would share the good news w/anyone interested in new paradigms of diabetes care including acceleration of the clinical trials process for new cures, new cure therapies and new devices to assist people with tight blood sugar control.

Announcing the SWEETKIDSNETWORK

Check it out online at www.sweetkidsnetwork.org and check back often to see progress announcements and to find out about research trials looking to recruit patients from the Sweet Kids Network.