Association between number of months below K/DOQI haemoglobin target and risk of hospitalization and death

Background. A proportion of haemodialysis patients experience periods below target haemoglobin levels due to longer time required to reach the target or to haemoglobin level variability. We aimed to determine the consequences associated with cumulative number of months below target haemoglobin concentrations. Methods. We constructed an incident cohort including patients whose day 91 after dialysis initiation fell between 1 January and 31 December 2002. Haemoglobin concentration, erythropoiesis-stimulating agent dose, comorbid condition and hospitalization data were obtained from Medicare claims. Patients were classified by 0, 1, 2 or 3 months with haemoglobin concentration below the K/DOQI target (11 g/dL). Using an inverse probability weighted marginal structural model to adjust for time-varying factors associated with haemoglobin concentration, we determined the association between number of months below target and subsequent risk for hospitalization and mortality. Results. The final cohort included 54 328 patients who met criteria. Those with more months below haemoglobin target were less likely to have received intravenous iron. More months below target were associated with increased risk of hospitalization (RR 1.70, 95% CI 1.63-1.76) and mortality (RR 2.48, 95% CI 2.28-2.69). Conclusions. Future interventions should focus on modifiable factors associated with greater time below target haemoglobin concentrations to determine whether altering the time below target can alter the risk of hospitalizations or mortality.