Treating anemia at different stages of renal disease.

Cardiovascular disease is the leading cause of the poor long-term survival of patients with chronic kidney disease (CKD). Anemia, which is a frequent and early complication of CKD, not only impairs patients' quality of life, but also is an independent risk factor for adverse cardiovascular outcomes. This may be due to its impact on cardiac function leading to the development of left ventricular hypertrophy. Starting from the clear association between higher hemoglobin levels and better outcomes found in observational surveys, a number of interventional studies have been designed to verify whether correcting anemia fully improves patient outcomes. The results have not indicated any major effect, although the majority of the studies were not primarily designed to test the effect of anemia correction on mortality. This is especially true in the case of CKD patients not undergoing dialysis. Many of these studies have also suffered from relatively short follow-up periods and from the fact that their statistical power was reduced because the difference in achieved hemoglobin levels between the experimental and control groups was often less than expected. Further studies aimed at better investigating the complex mechanisms underlying responsiveness to erythropoiesis-stimulating agents will probably help to explain the disagreement between observational studies and randomized clinical trials.