Hemoglobin A1C Accuracy Questioned-Again

03/12/08 Treatment Options

By Corie Richter

For about six years researchers have been questioning accuracy of the hemoglobin A1C test—long thought to be the “gold standard” in blood sugar measurement.

Wake Forest University Baptist Medical Center conducted a study using a newer test based on albumin glycolation as opposed to hemoglobin A1C and found a considerable difference in results. They found the hemoglobin A1C test loses its accuracy for diabetics on dialysis.

Diabetics on hemodialysis are particularly prone to death. Twenty-three percent die within the first year of treatment from infection and heart disease complications. Only 31 percent survive more than five years. Better glucose measurement may lead to improved blood sugar control and health.

The difference in accuracy may lie in how albumin glycolation measures glucose. It is a good measure of blood sugar over the previous month, rather than the last three months like the A1C test. To understand the problem, we need to look at cell biology.

Extra glucose in the body seeps into the blood stream. Hemoglobin from red blood cells reacts with glucose. It also carries oxygen from the lungs through the body. By measuring hemoglobin levels patients medical professionals measure how much glucose has been present in the blood over the last three months.

Research published in the journal Kidney International suggests that dialysis actually stresses hemaglogin carrying red blood cells, causing their premature death. Consequently there is less hemoblobin present in the blood of dialysis patients, and hemoglobin A1C measures would naturally be lower.

In this study participants from the Wake Forest study were diabetic hemodialysis patients. In dialysis, hemaglogin-carrying red blood cells don't survive as long. So an undermeasurement may occur when the test detects less hemoglobin in a patient's blood. It is unclear whether the results translate into the general population of diabetics because of the nature of dialysis.

The glycated albumin test may be more accurate for the dialysis population. Testing based on albumin's reaction with glucose measures results for the previous 30 days—when the red blood cells are still alive and functioning.

We can understand why the A1C test may not reflect glucose status well for dialysis patients. Whether the albumin test is superior for all diabetics is an issue that remains open until ongoing studies are concluded.

Source:

Kidney International, February 2008