Diabetics on Dialysis Do Better With Higher Hemoglobin A1c

Daniel M. Keller, PhD

November 22, 2011

November 22, 2011 (Philadelphia, Pennsylvania) — Using data from the international Dialysis Outcomes and Practice Patterns Study (DOPPS), researchers have discovered that the desirable range for glycated hemoglobin (HbA1c) levels is higher for diabetic patients on dialysis than guidelines recommend for the general diabetic population.

Both high and low levels were associated with an increased risk for death, Fritz Port, MD, MS, senior research scientist at Arbor Research Collaborative for Health in Michigan, reported here at Kidney Week 2011: American Society of Nephrology 44th Annual Meeting.

More than half the patients on dialysis in the United States have diabetes, so these findings affect a substantial number of people, Dr. Port pointed out.

The aim of DOPPS is to discover which dialysis practices result in the best patient outcomes. It has accumulated data on more than 38,000 patients from a representative and random sample of hemodialysis centers and patients in 12 countries.

The study involved 6383 patients with diabetes on hemodialysis who had at least 2 determinations of HbA1c during the first 8 months. In their analysis, the investigators adjusted for factors that could affect mortality, such as age, sex, years on dialysis, poor nutrition, and country of residence.

"The range from 6% to 9% seems to be the lower range of risk. There's even an impression that you could say that from 7% to 9% is the lowest risk," Dr. Port said. The graph of hazard ratios for mortality forms a U-shaped curve, with higher mortality at the lowest and highest levels of HbA1c. Current recommendations for the general diabetes population specify that patients try to keep their HbA1c levels below 7%.

Mortality Risk by Level of HbA1c

HbA1c range (%) Estimated Hazard Ratio
<5.0 1.35
5.0–5.9 1.20
6.0–6.9 1.10
7.0–7.9 1.00 (reference)
8.0–8.9 0.95
≥9.0 1.30

When the researchers examined the medication records of the diabetic patients on hemodialysis, they found that 46% of those with HbA1c levels below 7% were taking oral drugs or insulin. Of the patients with levels of 9% or greater, 31% were not taking antihyperglycemic drugs.

"It shows the opportunities to improve patient care by either decreasing the amount of medications in those with low hemoglobin A1c or increasing the use of medications in those with a high hemoglobin A1c," Dr. Port explained.

On the basis of this study and others like it, he said, the guideline recommendations for HbA1c levels for diabetics "will likely be changed for dialysis patients, but they're not finalized yet."

Katherine Tuttle, MD, executive director of research at the Providence Sacred Heart Medical Center and professor of medicine at the University of Washington School of Medicine in Spokane, who was not involved in the study, told Medscape Medical News that the guidelines will be going out for public comment soon, probably in the next couple of months. She chairs the work group developing new clinical practice guidelines for diabetes and chronic kidney disease.

"I think it's fair to say that the recommendation for an A1c of about 7% or less will stand for people with new-onset diabetes who are relatively young and [who have] limited comorbidities," she said. Although she cannot be specific about what the guidelines will include, she did say: "I think the guidelines will really promote individualizing therapy.... For people who are at high risk of hypoglycemia, which is most people with advanced chronic kidney disease or with limited life expectancy and multiple comorbidities, clinicians should consider a more liberal target."

Besides treatment advice, the guidelines will have a series of research recommendations. "One of them is that long-term glycemic control, such as A1c, needs to be validated in people with advanced kidney disease, or really any kidney disease, because people with any kidney disease were excluded from the original validation studies," Dr. Tuttle said. An important area of future research is other markers of glycemic control, such as glycated albumin, "because it's not affected by red cell turnover and other abnormalities in hemoglobin," she explained.

"We shouldn't limit our scope of research.... We should be looking for better markers, particularly for this population," she advised.

DOPPS is supported by research grants from Amgen, Kyowa Hakko Kirin (in Japan), Genzyme, Abbott, and Baxter without restrictions on publications. Dr. Port is an employee of Arbor Research Collaborative for Health. Dr. Tuttle has disclosed no relevant financial relationships.

Kidney Week 2011: American Society of Nephrology 44th Annual Meeting. Abstract TH-OR065. Presented November 10, 2011.


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