A new study from Wake Forest University Baptist Medical Center has found that the standard test for measuring blood-sugar control in diabetics may not be accurate for patients on kidney hemodialysis.
The Baptist researchers said they found that the hemoglobin A1C test did not provide a "true glucose control" in hemodialysis patients.
Hemodialysis works by passing blood through an artificial kidney machine for cleansing. It is used in cases of kidney failure.
The researchers said that the test "could give false comfort to patients and physicians" because diabetic dialysis patients still might have unacceptably high blood sugars.
"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.
"This was a surprise to the nephrology community. The test we've all come to accept as 'the gold standard' has proven to be inaccurate in this patient population," he added.
HbA1c measures the percentage of hemoglobin that has reacted with glucose. This measure, also known as glycosylated hemoglobin, reflects blood sugar control over the previous 30-120 days.
Researchers evaluated 307 patients with diabetes - 258 with end-stage kidney disease on hemodialysis and 49 who did not have kidney failure.
The team compared the standard HbA1c test with a newer test (glycated albumin, or GA) that measures the amount of blood sugar that has reacted with albumin, a protein in the plasma. The GA test reflects blood sugar control over the previous three to four weeks. Blood samples were also analyzed to determine recent blood sugar levels.
Compared to those without kidney failure, diabetic patients on hemodialysis had higher blood sugars and GA levels, despite paradoxically lower HbA1c results. The relationship between GA and HbA1c differed between diabetic dialysis patients and those without kidney disease, demonstrating that the HbA1c did not accurately reflect blood sugar control in those on hemodialysis.
Researchers believe the major reason for the discrepancy is that HbA1c depends on red blood cell survival and these cells don't live as long in hemodialysis patients. Most dialysis patients have anemia requiring treatment with medications that stimulate red blood cell production (erythropoietin).
The research has been reported in Kidney International, the journal of the International Society of Nephrology.