Implementing the 2017 VA/DoD Diabetes Clinical Practice Guideline

David C. Aron, MD, MS. The identification of HbA_1c has been a tremendous advance in our ability to manage patients with diabetes. It represents an average blood glucose over the preceding 3 months but like everything in this world, it has issues. One is the fact that there is a certain degree of inaccuracy in measurement, and that’s true of any measurement that you make of anything. Just as you allow a little bit of wiggle room when you’re driving down the New Jersey Turnpike and watching your speedometer, which is not 100% accurate. It says you are going 65 but it could, for example be 68 or 62. You don’t want to go too fast or you’ll get a speeding ticket. You don’t want to go too slowly or the person behind you will start honking at you. You want to be at the speed limit plus or minus. The first thing to think about in using HbA_1c is the issue of accuracy. Rather than choose a specific target number, health care providers should choose a range between this and that. There’ll be more detail on that later.

The second thing is that part of the degree to which HbA_1c represents the average blood glucose depends on a lot of factors, and some of these factors are things that we can do absolutely nothing about because we are born with them. African Americans tend to have higher HbA_1c levels than do whites for the same glucose. That difference is as much as 0.4. An HbA^_1c of 6.2 in African Americans gets you a 5.8 in whites for the same average blood glucose. Similarly, Native Americans have somewhat higher HbA_1c, although not quite as high as African Americans. Hispanics and Asians do as well, so you have to take your patient’s ethnicity into account.

The second has to do with the way that HbA_1c is measured and the fact that there are many things that can affect the measurement. An HbA_1c is dependent upon the lifespan of the red blood cell, so if there are alterations in red cell lifespan or if someone has anemia, that can affect HbA_1c. Certain hemoglobin variants, for example, hemoglobin F, which is typically elevated in someone with thalassemia, migrates with some assays in the same place as thalassemia, so the assay can’t tell the difference between thalassemia and hemoglobin F. There are drugs and other conditions that can also affect HbA_1c. You should think about HbA_1c as a guide, but no number should be considered to be written in stone.

Dr. Conlin. I can imagine that this would be particularly important if you were using HbA_1c as a criterion for diagnosing diabetes.

Dr. Aron. Quite right. The effects of race and ethnicity on HbA_1c account for one of the differences between the VA/DoD guidelines and those of the American Diabetes Association (ADA).

Dr. Conlin. Isn’t < 8% HbA_1c a national performance measure that people are asked to adhere to?

Dr. Aron. Not in the VA. In fact, the only performance measure that the VA has with a target is percent of patients with HbA_1c > 9%, and we don’t want any of those or very few of them anyway. We have specifically avoided targets like < 8% HbA_1c or < 7% HbA_1c, which was prevalent some years ago, because the choice of HbA_1c is very dependent upon the needs and desires of the individual patient. The VA has had stratified targets based on life expectancy and complications going back more than 15 years.

Dr. Conlin. Another issue that can confuse clinicians is when the HbA_1c is in the target range but actually reflects an average of glucose levels that are at times very high and very low. How do we address this problem clinically?

Dr. Aron. In managing patients, you use whatever data you can get. The HbA_1c gives you a general indication of average blood glucose, but particularly for those patients who are on insulin, it’s not a complete substitute for measuring blood glucose at appropriate times and taking the degree of glucose variability into account. We don’t want patients getting hypoglycemic, and particularly if they’re elderly, falling, or getting into a car accident. Similarly, we don’t want people to have very high blood sugars, even for limited periods of time, because they can lead to dehydration and other symptoms as well. We use a combination of both HbA_1c and individual measures of blood glucose, like finger-stick blood sugar testing, typically.

Dr. Conlin. The VA/DoD CPG differs from other published guidelines in that we proposed patients are treated to HbA_1c target ranges, whereas most other guidelines propose upper limits or threshold values, such as the HbA_1c should be < 7% or < 8% but without lower bounds. Dr. Colburn, what are the target ranges that are recommended in the CPG? How were they determined?

Maj. Jeffrey A. Colburn, MD. It may be helpful to pull up the Determination of Average Target HbA_1c Level Over Time table (page S17), which lays out risk for patients of treatment as well as the benefits of treatment. We first look at the patient’s state of health and whether they have a major comorbidity, a physiologic age that could be high risk, or advanced physiologic age with a diminished life expectancy. In controlling the levels of glucose, we’re often trying to benefit the microvascular health of the patient, realizing also that eventually poor management over time will lead to macrovascular disease as well. The main things that we see in child data is that the benefits of tight glucose control for younger patients with shorter duration of type 2 diabetes mellitus (T2DM) is the prevention of retinopathy, nephropathy, and peripheral neuropathy. Those patients that already have advanced microvascular disease are less likely to benefit from tight control. Trying to push glucose very low can harm the patient. It’s a delicate balance between the possible benefit vs the real harm.

The major trials are the ADVANCE, ACCORD, and the VADT trial, which was done in a VA population. To generalize the results, you are looking at an intensive control, which was trying to keep the HbA_1c in general down below the 7% threshold. The patients enrolled in those trials all had microvascular and macrovascular disease and typically longer durations of diabetes at the time of the study. The studies revealed that we were not preventing macrovascular disease, heart attacks, strokes, the types of things that kill patients with diabetes. Individuals at higher HbA_1c levels that went down to better HbA_1c levels saw some improvement in the microvascular risk. Individuals already at the lower end didn’t see as much improvement. What we saw though that was surprising and concerning was that hypoglycemia, particularly severe hypoglycemia in the VADT trial was a lot more frequent when you try and target the HbA_1c on the lower end. Because of these findings, we proposed the table with a set of ranges. As Dr. Aron noted, HbA_1c is not a perfect test. It does have some variance in the number it presents. The CPG proposed to give individuals target ranges. They should be individualized based upon physiologic age, comorbidities, and life expectancy.

A criticism of the table that I commonly hear is what’s the magic crystal ball for determining somebody’s life expectancy? We don’t have one. This is a clinician’s judgment. The findings might actually change over time with the patient. A target HbA_1c range is something that should be adapted and evolve along with the clinician and patient experience of the diabetes.

There are other important studies. For example, the UKPDS trials that included patients with shorter durations of diabetes and lesser disease to try and get their HbA_1c levels on the lower end. We included that in the chart. Another concept we put forward is the idea of relative risk (RR) vs absolute risk. The RR reduction doesn’t speak to what the actual beginning risk is lowered to for a patient. The UKPDS is often cited for RR reduction of microvascular disease as 37% when an HbA_1c of 7.9% is targeted down to 7.0%. The absolute risk reduction is actually 5 with the number needed to treat to do so is 20 patients. When we present the data, we give it a fair shake. We want individuals to guide therapy that is going to be both beneficial to preventing outcomes but also not harmful to the patient. I would highly recommend clinicians and patients look at this table together when making their decisions.

Dr. Conlin. In the VA/DoD CPG, the HbA_1c target range for individuals with limited life expectancy extends to 9%. That may seem high for some, since most other guidelines propose lower HbA_1c levels. How strong are the data that a person with limited life expectancy, say with end-stage renal disease or advanced complications, could be treated to a range of 8% to 9%? Shouldn’t lower levels actually improve life expectancy in such people?

Dr. Colburn. There’s much less data to support this level, which is why it’s cited in CPG as having weaker evidence. The reason it’s proposed is the experience of the workgroup and the evidence that is available of a high risk for patients with low life expectancy when they reduce their HbA_1c greatly. One of the concerns about being at that level might be the real issue of renal glycosuria for individuals when their blood glucose is reaching above 180 mg/dL, which correlates to the 8% to 9% HbA_1c range. You may have renal loss and risk of dehydration. It is an area where the clinician should be cautious in monitoring a patient in the 8% to 9% HbA_1c range. With that being said, a patient who is having a lot of challenges in their health and extremely advanced conditions could be in that range. We would not expect a reversing of a micro- or macrovascular disease with glycemia control. We’re not going to go back from that level of disease they have. The idea about keeping them there is to prevent the risks of overtreatment and harm to the patient.

Dr. Conlin. Since patients with diabetes can progress over their lifetime from no complications to mild-to-moderate complications to advanced complications, how does the HbA_1c target range evolve as a patient’s condition changes?

Dr. Colburn. As we check for evidence of microvascular disease or neuropathy signs, that evidence often is good for discussion between the clinician and patient to advise them that better control early on may help stem off or reverse some of that change. As those changes solidify, the patient is challenged by microvascular conditions. I would entertain allowing more relaxed HbA_1c ranges to prevent harm to the patient given that we’re not going back. But you have to be careful. We have to consider benefits to the patient and the challenges for controlling glucose.

I hope that this table doesn’t make providers throw up their hands and give up. It’s meant to start a conversation on safety and benefits. With newer agents coming out that can help us control glucose quite well, without as much hypoglycemia risk, clinicians and patients potentially can try and get that HbA_1c into a well-managed range.

Dr. Conlin. The CPG discusses various treatment options that might be available for patients who require pharmacologic therapy. The number of agents available is growing quite markedly. Dr. Colburn, can you describe how the CPG put together the pharmacologic therapy preferences.

Dr. Colburn. The CPG expressively stayed away from trying to promote specific regimens of medications. For example, other guidelines promote starting with certain agents followed by a second-line agent by a third-line agents. The concern that we had about that approach is that the medication landscape is rapidly evolving. The options available to clinicians and patients are really diverse at this moment, and the data are not concrete regarding what works best for a single patient.

Rather than trying to go from one agent to the next, we thought it best to discuss with patients using the SHARE decision-making model, the adverse effects (AEs) and relative benefits that are involved with each medication class to determine what might be best for the person. We have many new agents with evidence for possible reductions in cardiovascular outcomes outside of their glycemic control properties. As those evidences promote a potentially better option for a patient, we wanted to allow the room in management tomake a decision together. I will say the CPG as well as all of the other applicable diabetes guidelines for T2DM promote metformin as the first therapy to consider for somebody with newly diagnosed T2DM because of safety and availability and the benefit that’s seen with that medication class. We ask clinicians to access the AHRQ website for updates as the medicines evolve.

In a rapidly changing landscape with new drugs coming into the market, each agency has on their individual website information about individual agents and their formulary status, criteria for use, and prior authorization requirements. We refer clinicians to the appropriate website for more information.

Dr. Conlin. There are a series of new medications that have recently come to market that seem to mitigate risk for hypoglycemia. Dr. Lugo, which treatment options carry greater risk? Which treatment options seem to have lesser risk for hypoglycemia?

Amy M. Lugo, PharmD. Insulin and the sulfonylureas have the highest risk of hypoglycemia. The sulfonylureas have fallen out of favor somewhat. One reason is that there are many newer agents that do not cause weight gain or increase the risk of hypoglycemia. Some of the newer insulins may have a lower risk of hypoglycemia and nocturnal hypoglycemia, in particular; however, it is difficult to conclude emphatically that one basal insulin analog is less likely to cause clinically relevant severe or nocturnal hypoglycemia events. This is due to the differences in the definitions of hypoglycemia used in the individual clinical trials, the open label study designs, and the different primary endpoints.