Summary

While setting a target for HbA1c below 7% may be suitable for most type 2 diabetics, recommendations from an American College of Physicians committee add the need to take the patient's individual status (diabetic complications, additional conditions, life expectancy, and the patient's preferences) into consideration.

Introduction

Good control of blood sugar in patients with diabetes results in a reduced chance of their development of complications, such as blindness, kidney failure, nerve damage, heart disease, and stroke. Many diabetics use glucometers to test their blood sugar at appropriate intervals, so that they can adjust their antidiabetic medication accordingly. The problem is that blood glucose level readings only give a snapshot view of the state of glucose metabolism. A test called the hemoglobin-A1c (HbA1c) measures blood sugar control over the previous 3 months; so lower HbA1c levels mean better control of diabetes.¹

There has recently been a meeting of the world experts on HbA1c measurement, to iron out differences in testing methodology.² It was concluded that the only valid system of measurement is that of the International Federation of Clinical Chemistry, with results reported in mmol/mol. The percentage HbA1c should be derived from this, and designated the "A1c-derived average glucose" or ADAG. In practical terms, it seems likely that HbA1c expressed as a %age of the total hemoglobin will continue to be used - as, for example, in the guidance statement issued about HbA1c target levels, which we shall discuss below.

Background

Accepting that HbA1c gives a much better picture of overall glucose control over the previous 3 months, several organizations have developed recommendations for target HbA1c values for patients with type 2 diabetes, giving them and their physicians an objective to aim for in determining treatment, whether its diet, exercise, antidiabetic drugs, or all three.

The American College of Physicians charged their Clinical Efficacy Assessment Subcommittee to develop recommendations about setting HbA1c targets, and has now published these in the Annals of Internal Medicine.

Guidelines that address blood sugar control in type 2 diabetic patients were examined from the following 9 sources:

• American Association of Clinical Endocrinologists
• American Academy of Family Physicians
• American Diabetes Association
• American Geriatrics Society
• Canadian Diabetes Association
• Institute for Clinical Systems Improvement
• National Institute for Health and Clinical Excellence
• Scottish Intercollegiate Network
• Veterans Health Administration

An appraisal instrument (the Appraisal of Guidelines, Research, and Evaluation in Europe [AGREE] was used to evaluate the above guidelines. All the guidelines except that from the American Academy of Family Physicians specified HbA1c target levels - mostly these were about 7%. However, several guidelines recommended customizing the target to the individual patient. For instance, lower targets would be appropriate for people at high risk of diabetic complications, and higher targets used for people with limited life expectancy because of other disease or advance age.

The Committee's Recommendations

After their review of the available English language guidelines, the ACP committee made the following 3 recommendations:

1. The benefits and harm of specific levels of glucose control should be discussed fully between patients and their physicians. Patients should aim for an HbA1c level as low as possible without causing unacceptable or frequent episodes of low blood sugar ('hypoglycemia'), in order to avoid the complications of diabetes. An HbA1c level below 7% is a reasonable goal for many, but not all patients.

2. Individualized evaluation of the risk for complications, additional conditions (comorbidity), life expectancy, and patient preferences should guide the specific target for HbA1c.

3. Further research is needed to determine the optimal level of glucose control, particularly in patients with additional medical conditions.

Conclusions

The Committee's recommendations are not world-shattering. Most diabetologists would have reached similar conclusions, unaided by a study of 9 different guidelines. However, they do provide a message for physicians, namely to avoid driving a patient to reach a maybe unattainable target. Rather, the target should be set mutually with the patient, taking the patient's knowledge, health, and preferences into consideration.