The role of HbA1C testing in diagnosing diabetes

Lee, Hyejin

Abstract

Diabetes is often not diagnosed until complications appear, and approximately 30% of people with diabetes may be undiagnosed. Also, complications of diabetes have become a leading cause of impairment of life quality. Therefore efficient approaches to diagnosing diabetes should be developed. The most widely used test for diagnosis of diabetes includes fasting plasma glucose (FPG) and the oral glucose tolerance test(OGTT). The international expert committee has recently recommended the use of HbA1C assay to diagnose diabetes, with a threshold of > or = 6.5%. In 2010, the American Diabetes Association (ADA) adopted the proposal and it became part of the diagnostic criteria of diabetes in the 2010 Clinical Practice Recommendations. Previously, HbA1C had been used primarily to monitor glycemic control among individuals with diabetes. However, over the last decade, the HbA1C measurement has become standardized, facilitating its recognition as an acceptable diagnostic method for diabetes. And several practical considerations favor the use of HbA1C in diagnosing diabetes. The HbA1C does not require the patient to be fasting, can be done at any time that a visit is scheduled, is simpler to perform than the 2 hr OGTT, and is less dependent on the patient's health status at the moment of the blood draw. Also HbA1C is less sensitive to several preanalytical variables, and biological variability is lower than that of both 2 hr post-load glucose and FPG. However, this advantage must be balanced by the low sensitivity of HbA1C, the limited standardization of HbA1C in certain regions, the incomplete correlation between HbA1C and glucose, and risk of misdiagnosis in patient with increased red blood cell turnover, end stage renal disease, with certain forms of hemoglobinopathies.