Is HbA1c A Reliable Test In Patients With Diabetes And Renal Disease?
- Volume 22 - Issue 8 - August 2009
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Reportedly 23.6 million individuals in the United States (or 8 percent of the American population) are affected by diabetes.1 Many of those with diabetes will develop related comorbidities such as microvascular pathology in the retina, renal glomeruli and peripheral nerves. Other comorbidities include accelerated atherosclerotic microvascular disease affecting arteries that supply the heart, brain and lower extremities.2,3
Controlled clinical trials in patients with type 2 diabetes have established that rigid glycemic control results in improved long-term outcomes and a decreased incidence of diabetic complications.4,5 Further, many studies have demonstrated a strong correlation among mean levels of glycemia, measured as glycated hemoglobin A1c (HbA1c), and diabetic complications.1
Collectively, this body of knowledge provides the foundation for the recommended treatment goals from the American Diabetes Association (ADA) of maintaining HbA1c at less than 7%. However, only one-third of patients with diabetes achieve this goal and even less reach the target level of 6.5% HbA1c that the American College of Endocrinology promotes.2
Other clinical evidence indicates favorable effects on cardiovascular disease in those with tight glycemic control. As we know, cardiovascular disease is a main cause of death in patients with diabetes. Strict glycemic control is reportedly a strong prognostic indicator for patients who have diabetes with chronic kidney disease (CKD) requiring hemodialysis.5
Establishing the relationship between HbA1c and glycemic control in this group of individuals is essential because of the fact that almost half of all end-stage renal disease (ESRD) patients on dialysis in the U.S. are affected by diabetes. Unfortunately, few studies examine the association between HbA1c and clinical outcomes in the dialysis patient.3
With these trends and considerations in mind, let us take a closer look at the reliability of HbA1c in patients with diabetes and renal disease.
What You Should Know About HbA1c
Management of glycemic control is of utmost importance in all patients with diabetes. Currently, we diagnose diabetes by using fasting plasma glucose and the oral glucose tolerance test.6 Currently, researchers are looking at the measurement of glycated proteins.4 Glycated hemoglobin has became the mainstay of evaluating long-term glycemic management as both a screening and diagnostic tool, and appears to be on the brink of official recognition as the preferred diagnostic test for diagnosing diabetes.6
We are already using this value for patient education and counseling, for feedback about diabetes control, to improve patient motivation and to monitor management.7 Measurement of HbA1c also aids in the evaluation of the risk of diabetic complications.8 Mitka notes the thoughts of the ADA, the European Association for the Study of Diabetes and the International Diabetes Federation proposing the use of HbA1c as the preferred diagnostic test for diabetes.6,9
Although there is no international standard for determining HbA1c and various methods are available for its collection, strides continue toward creating a more standardized approach to its measurement.7 Typically, HbA1c is measured via high performance liquid chromatography and immunoassay.4,7 The percent HbA1c of glycated hemoglobin provides an estimation of blood glucose levels over a three- to four-month period.7 This laboratory test is favorable to previous methods due to its ease of use. Accordingly, this test may facilitate earlier diagnosis of patients with diabetes and potentially lead to fewer diabetes-associated complications.6