A new indicator of variations in hemoglobin level over time is a strong predictor of the risk of death among patients receiving dialysis for end-stage renal disease (ESRD), reports a study in the December Journal of the American Society of Nephrology.
"Hemoglobin variability—a measure of the stability of levels of hemoglobin among chronic hemodialysis patients—provides a novel way of thinking about and understanding the relationship between anemia and outcomes in ESRD," comments Dr. Harold I. Feldman of University of Pennsylvania School of Medicine, Philadelphia, one of the study authors.
The researchers used data on nearly 35,000 dialysis patients to analyze the effects of hemoglobin variability on the risk of death. They focused on a newly developed metric, termed “Hb-Var,” that measures variability in hemoglobin levels independent of their absolute values and trends over time.
Hemoglobin is the oxygen-carrying compound in the blood. Anemia, or low hemoglobin levels, is one of the most frequent complications of kidney failure and a common cause of death in dialysis patients. Treatment including erythropoietin and intravenous iron has been a major advance in the management of kidney failure-related anemia, yet low blood counts and variation in hemoglobin levels continue to be a problem for many dialysis patients.
The new study found that high Hb-Var scores—indicating greater hemoglobin variability—predicted a higher risk of death in dialysis patients. For each 1 g/dL (gram per deciliter) increase in Hb-Var, the risk of death increased by 33 percent, after adjustment for other factors.
The relationship between Hb-Var and mortality remained significant even after adjustment for absolute hemoglobin levels and trends in hemoglobin levels over time. Higher Hb-Var scores predicted an increased risk of death in nearly all subgroups of dialysis patients. "As postulated, higher levels of hemoglobin variability were associated with higher rates of death," says Dr. Feldman.