Hemoglobin A1c Controversy Déjà vu
Hemoglobin A1c (HbA1c) refers to a minor population of hemoglobin A that has been modified by attachment of glucose to the N-terminal amino acid of the beta globin chain. Since erythrocytes are freely permeable to glucose, the attachment occurs continually over the entire lifespan of the erythrocyte and is dependent on glucose concentration and the duration of exposure of the erythrocyte to blood glucose. HbA1c is a weighted average of blood glucose levels during the preceding 120 days, which is the average life span of red blood cells. A normal HbA1c level in people without diabetes is less than 5.7%.
There is broad consensus that HbA1c levels should be used for routine care of all patients with diabetes mellitus. Baseline HbA1c levels are strongly related to the incidence and/or progression of retinopathy, gross proteinuria, and loss of tactile sensation or temperature sensitivity. In 2009, the American Diabetes Association (ADA) recommended an HbA1c goal for nonpregnant adults of less than 7% (Diabetes Care 2009;32(S1):S3-S5).
The American College of Physicians (ACP) is the largest US medical specialty organization and is composed mainly of primary care internists, who regularly take care of patients with diabetes. The Clinical Guidelines Committee of ACP recently published updated gudelines for HbA1c targets for glycemic control in patients with type 2 diabetes. These new guidelines state that clinicians should personalize glycemic goals and aim to achieve an HbA1c level between 7 and 8% for most patients with type 2 diabetes.
ACP’s new statement is at odds with the American Diabetes Association (ADA) that recommends a HbA1c goal of 7%, while the American Association of Clinical Endrocrinologists (AACE) supports even lower HbA1c levels of 6.5% if it can be achieved safely. These professional organizations expressed concern that ACP’s relaxed HbA1c target would mitigate the benefits of tight glycemic control such as reduced microvascular complications.
ACP recognizes that intensive glycemic control poses a serious risk of hypoglycemia for patients with type 2 diabetes. Overtreatment can reduce patient’s quality of life, especially those who are managing multiple chronic diseases and taking multiple medications. ACP appears to be trying to strike a reasonable balance between the benefits and harms of glycemic control. This balance may also decrease patient's financial burden and increase compliance.
References
Qaseem A, Wilt TJ, Kansagara D, Horwitch C, Barry MJ, Forciea MA; Clinical Guidelines Committee of the American College of Physicians. Hemoglobin A1ctargets for glycemic control with pharmacologic therapy for nonpregnant adults with type 2 diabetes mellitus: a guidance statement update from the American College of Physi- cians. Ann Intern Med. 2018;168:569-76. [PMID: 29507945] doi:10 .7326/M17-0939.
Abbasi J. For Patients with Type 2 Diabetes, What’s the best target hemoglobin A1c? JAMA published online May 30, 2018.
Draznin B. et al. Guidelines versus guidelines: What’s best for the patient? Ann Intern Med. doi:10.7326/M18-0939.
