The standard test for measuring blood sugar control in people with diabetes is not accurate in those on kidney hemodialysis, according to new research at Wake Forest University Baptist Medical Center.

Wake Forest investigators reported in Kidney International that the hemoglobin A1c test (HbA1c) underestimates true glucose control in hemodialysis patients and could give false comfort to patients and physicians. Hemodialysis, in which blood is passed through an artificial kidney machine for cleansing, is used in cases of kidney failure.

"These results suggest that the nearly 200,000 diabetic hemodialysis patients in the United States who use this test may not be receiving optimal care for their blood sugar," said Barry I. Freedman, M.D., senior author and a professor of internal medicine and nephrology.

Diabetic dialysis patients who believe their blood sugars are in the ideal range may still have unacceptably high blood sugars. "This was a surprise to the nephrology community," said Freedman. "The test we've all come to accept as 'the gold standard' has proven to be inaccurate in this patient population."

HbA1c measures the percentage of hemoglobin (a protein in red blood cells) that has reacted with glucose. This measure, also known as glycosylated hemoglobin, reflects blood sugar control over the previous 30-120 days.