Anemia treatment in chronic kidney disease: shifting uncertainty.

Epidemiologic observations showing associations between higher levels of some biologic markers such as blood pressure and serum cholesterol with heightened risk of death and non-fatal cardiovascular events have provided important data to develop hypotheses regarding pharmacologic therapies to modify these markers to improve prognosis. Randomized controlled trials have shown that strategies to reduce blood pressure with a variety of antihypertensive agents and LDL cholesterol with statins do, indeed, result in important improvements in clinical outcomes. However, there are several instances where a hypothesis based on strong observational data has been rejected based on surprising counterintuitive evidence generated from randomized controlled clinical trials. Use of inotropic therapies for patients with reduced left ventricular ejection fraction heart failure, administration of class I antiarrhythmic agents to suppress ventricular arrhythmias in high-risk patients, and use of hormone replacement therapy for postmenopausal women have each shown that therapies presumed to be of benefit may actually be producing unfavorable clinical results. Use of erythropoietic stimulating agents (ESA) in chronic kidney disease patients with anemia is similarly based on strong observational data indicating that the degree of anemia is independently associated with higher risk for cardiovascular morbidity and mortality. In non-dialysis patients with mild to moderate anemia, current clinical outcome studies have only addressed arbitrary hemoglobin targets for ESA therapy and have shown that targeting the higher hemoglobin levels was not associated with the benefit and may even result in harm. This review will outline the importance of having a placebo-controlled trial in this patient population to better assess the risk benefit profile of this therapy.