Comparative effectiveness of calcium-containing phosphate binders in incident U.S. dialysis patients.

BACKGROUND AND OBJECTIVES Few studies have assessed the association between phosphate binder use and hard outcomes in dialysis patients. Furthermore, the comparative effectiveness of calcium carbonate and acetate is untested. We studied the association between use versus nonuse of calcium-containing phosphate binders (CCPBs) and mortality from any cause. We also tested whether mortality differed among users of individual CCPBs. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS A nationally representative prospective cohort of incident U.S. dialysis patients (1996 to 1997), assembled before the availability of sevelamer and lanthanum, was used. Use of each CCPB was ascertained from chart abstraction records. A large number of sociodemographic, clinical, and laboratory characteristics were available for confounding control in multivariate and propensity score-matched Cox regression models. RESULTS Among 3603 incident dialysis patients, 77.5% used a CCPB, whereas 22.5% did not. Baseline use of CCPB was associated with an adjusted 19% lower mortality rate among CCPB users compared with nonusers. With successful matching of 800 exposed and nonexposed individuals on their exposure propensity score, however, CCPB users and nonusers had similar mortality. No mortality differences were observed between calcium acetate and calcium carbonate users in crude, adjusted, or propensity-matched analyses. CONCLUSIONS No association was found between CCPB use and 1-year mortality in incident dialysis patients; choice of calcium carbonate versus acetate was also not associated with this outcome. Randomized trials are necessary to understand whether the prevailing practice of phosphate-binding therapy actually reduces adverse clinical outcomes.