To the Editor: Given clinical trial evidence that there is little or no benefit gained by raising hematocrit levels above approximately 30% (or perhaps even a lower target),1 we were puzzled to read the study by Dr Brookhart and colleagues2 suggesting that greater erythropoiesis-stimulating agent (ESA) dosage was associated with decreased mortality risk among ESA-resistant patients. There are 2 reasons that misclassification of the study exposure might have produced these findings.
Zhang Y, Thamer M, Cotter D. Anemia Management and Mortality Risk in Incident Hemodialysis Patients. JAMA. 2010;304(1):41-43. doi:10.1001/jama.2010.889