HbA1C Test Ineffective in Diabetic Dialysis Patients

Researchers at the Wake Forest Baptist Medical Center performed a study proving that the hemoglobin A_1c (HbA_1c) test, the most commonly used glucose monitoring test for patients with diabetes, is ineffective in diabetic dialysis patients.

The HbA_1c test is used by physicians to measure an individual’s average blood sugar level over a three month period; it is also the most commonly used long-term blood sugar test, and is extensively relied on in the medical community.

The American Diabetes Association has previously deemed the HbA_1c test an effective tool for diagnosing diabetes, but recently it has come under scrutiny for its ineffectiveness in managing patients with diabetes as well as advanced kidney failure. Kidney doctors argue that another test, the glycated albumin (GA assay), seems to perform far better in comparison for these specific patients.

“Many organs don’t function properly in severe kidney failure,” said Barry I. Freedman, M.D., John H. Felts III Professor and lead investigator. “For example, most dialysis patients have anemia with fewer red blood cells than they should, which has a dramatic impact on the accuracy of the HbA_1c reading.”

The HbA_1ct test results are only accurate when red blood cells—which carry hemoglobin and oxygen—have a normal lifespan, but dialysis patients possess shorter red cell survival. This factor reduces the time that sugar in the bloodstream has to interact with hemoglobin, which is what the test measures and thus causes lower HbA_1c values.

The GA test was created by the Tokyo-based Asahi Kasei Pharma Corporation. It measures blood sugars in a patient from over the past seventeen days, as opposed to the three month time period the HbA_1c measures. In occurrences where rapid changes take place in blood sugar, the GA provides a more exact depiction of diabetes control.

“Doctors long thought the HbA_1c predicted outcomes in diabetes,” Freedman said. “This test is not predictive of outcomes in diabetes patients with kidney disease on dialysis. Dialysis patients and physicians get a false sense of security because their lower HbA_1c actually relates to shorter red cell survival, yet suggests diabetes control is better than it really is.”

Freedman and researchers at the Wake Forest Baptist Medical Center assessed 444 patients with diabetes undergoing dialysis. The participants continued their normal treatment and HbA_1c monitoring; in addition, they agreed to undergo the GA test every three months for an average of more than 2.3 years.

The researchers then compared the results from the HbA_1c and GA tests to evaluate the ability of each test to predict hospitalizations and survival.

They found that the HbA_1c failed to predict these important medical outcomes; in comparison, the GA was a strong predictor of patient survival and hospitalizations.

“This is the first study showing that a blood sugar test predicts risk of death in diabetic dialysis patients, as well as risk of hospitalization,” Freedman said. “This test provides the missing link that will allow dialysis patients and physicians to accurately gauge risk. The association is clear: high GA readings predict higher risk.”

Freedman warns physicians not to rely solely on the HbA_1c in dialysis patients; instead, he suggests, doctors should directly monitor blood glucose levels multiple times per day until the GA test is available in America. At the moment, the GA test is available only in Japan, China and South Korea; the FDA has yet to approve it for the United States.

Almost 500,000 people are on dialysis in the Unites States and in 50% of these cases, diabetes is the cause of kidney failure.

Each year, over 20% of dialysis patients die, and with diabetes as the leading causes worldwide for kidney failure, there is a dire need for precise blood sugar testing in diabetic dialysis patients.

The study appears online in the Clinical Journal of the American Society of Nephrology.