Q: My patients with diabetes have different targets for their A1c and self-monitoring blood glucose goals. How are these targets determined?

Every year, the American Diabetes Association (ADA) convenes a group of experts to review the most recent evidence to determine the standards of medical care in diabetes. Glycemic targets are specifically reviewed and recommendations made in section 6 of the document Standards of Medical Care in Diabetes - 2018 (ADA, 2018). These recommendations are incorporated throughout our discussion here.

Providers and patients assess effectiveness and safety of treatment through A1c, self-monitoring of blood glucose (SMBG) and continuous glucose monitoring. Each patient's unique history of diabetes, comorbidities, age, and personal preference should be considered when glycemic targets and frequency of testing are determined. Cardiovascular disease is the primary cause of death for patients with diabetes and as such, understanding the impact of diabetes management on the complication of macrovascular disease (i.e., cardiovascular disease) is important. For patients with type 1 diabetes, there is evidence that intensive control early in the disease decreases macrovascular complications. This decrease in cardiovascular complications appears to persist for decades after successful intensive control. In patients with type 2 diabetes, there is evidence that intensive control early at diagnosis may decrease cardiovascular complications over time. In other studies, patients with type 2 who have multiple comorbidities and long-standing diabetes did not show a decrease in complications; and in fact, intensive control may have contributed to macrovascular events (ADA, 2018). So, it appears that there is a time for intense treatment and a time for more relaxed goals.

A1c is an indirect measure of blood glucose that reflects average blood glucose over 3 months and is predictive of complications. Those who have achieved glycemic goals should continue to be tested 2x/year for monitoring purposes. A1c should be tested quarterly for those who have not achieved glycemic goals or when therapy has changed. Those who are intensively managed, such as a pregnant woman with type 1 diabetes, may be tested more frequently than every 3 months. These decisions are based on the individual patient's clinical situation, the treatment regimen, and provider judgment. Point-of-care testing allows for timely treatment changes (ADA, 2018).

A1c targets take the patient status into consideration. For most patients, a goal of A1c <7% is appropriate. For some patients, more stringent goals (<6.5%) may be appropriate if this can be achieved without hypoglycemia or polypharmacy. This may include patients with short duration of diabetes, patients with type 2 diabetes on lifestyle only or metformin, long life expectancy, and no significant cardiovascular disease. Less stringent goals (<8%) may be used for those with severe hypoglycemia, limited life expectancy, advanced micro/macrovascular conditions, extensive comorbid conditions, and long-standing diabetes where the goal has been difficult to achieve even with education, SMBG, and medication regimes. The greatest number of microvascular complications (i.e., eye, nerve, and kidney damage) can be averted by taking patients from poor control to fair/good control. Decreasing A1c from 7% to 6% further decreases these complications, although risk reduction becomes smaller (ADA, 2018). Select patients will benefit from this reduction as long as hypoglycemia is not a significant barrier.

There are limitations to the A1c measurement. Conditions that affect red blood cell turnover such as hemolytic and other anemias, end-stage renal disease, blood transfusions, drugs that stimulate erythropoiesis, and pregnancy can result in differences between the A1c and actual blood glucose. A1c may not reflect the actual blood glucose when there is extreme variability. For example, a patient who has wide swings in blood glucose from hypoglycemia to hyperglycemia can have an A1c in a good range that is not indicative of their actual control. Studies have identified that A1c may overestimate or underestimate blood glucose levels. A few studies identified higher A1c in African-American patients in relation to their SMBG. More studies are needed particularly in the area of children and ethnic groups to clearly define these associations. In the meantime, use of A1c with SMBG is recommended (ADA, 2018).

Monitoring SMBG with A1c can confirm the accuracy of A1c as well as the accuracy of the meter and SMBG testing. Reviewing the SMBG patterns can identify that the pre- and postprandial results are truly reflective of the A1c result. Patients using intensive therapies like multiple-dose insulin and pumps should test before meals and snacks, bedtime, occasionally postprandially, before activities like driving, before exercising, when low blood sugar is suspected, and then after treatment until blood glucose is normal. These results are important for day-to-day direction of self-management. Among patients with type 1 diabetes, there is a correlation between frequent SMBG and lower A1c and fewer acute complications (ADA, 2018).

SMBG can also be helpful to guide treatment and self-management for patients with type 2 diabetes taking less-intensive insulin or oral medications. For this group, there is evidence of associated lowering of A1c in the first 6 months and that more frequent monitoring is associated with lower A1c (ADA, 2018). SMBG can guide patients in lifestyle management of nutrition and activity, as well as adjusting medications, especially related to prandial blood sugars and preventing hypoglycemia.

For SMBG to be effective, accuracy must be assured from the meter and the user. Checking meter accuracy and technique is important initially and at intervals thereafter. Using the results to guide self-management and clinical management is important. In 2015, SMBG targets were updated to reflect the importance of preprandial glucose levels on A1c, as well as the importance of avoiding hypoglycemia. Preprandial goals are typically set 80 to 130 mg/dL and <180 mg/dL peak postprandial (1-2 hours after the meal) (ADA, 2018). Providers adjust these goals based on the clinical picture of the patient.

Continuous glucose monitoring measures interstitial glucose (comparable to plasma glucose), and is a useful tool for those with type 1 diabetes, intensive therapies (including those with type 2 diabetes), and hypoglycemia unawareness. However, education, training, and support are critical for successful use of continuous glucose monitoring to affect A1c.

Determining the most effective tools to monitor glycemic control and specific targets is not a one-size-fits-all venture. Understanding the unique needs of each patient is critical in determining these aspects of care in order to achieve both short-term and long-term positive outcomes.

REFERENCE