title: Hematocrit was not validated as a surrogate end point for survival among epoetin-treated hemodialysis patients.
abstract: OBJECTIVE
  To evaluate the use of hematocrit as a surrogate end point for survival among end-stage renal disease (ESRD) patients treated with epoetin.
  
  
  METHODS
  Using United States Renal Data System (USRDS) data, we conducted an observational prospective study to analyze the relationships among epoetin dose, hematocrit, and survival for 31,301 facility-based hemodialysis patients incident to ESRD therapy in 1998. To address our objective, we used criteria developed by Prentice based on results from a Cox regression model.
  
  
  RESULTS
  Results indicate that hematocrit is inversely associated with epoetin dose. For the same epoetin treatment-related achieved hematocrit levels, there were widely varying treatment-related survival outcomes, thereby challenging a central criterion required to empirically validate a surrogate end point.
  
  
  CONCLUSIONS
  Our results support earlier clinical trial and epidemiological data suggesting that hematocrit may not be a valid surrogate for survival among the epoetin-treated renal failure population. We hypothesize that hematocrit may not be in the causal pathway or that epoetin may have important mechanisms of action apart from increasing hematocrit. Effective treatment for anemia may therefore not be simply a matter of increasing hematocrit. This study has potential implications for revising the existing treatment guidelines for anemia management and selecting an appropriate treatment regimen.
authors.affiliation: Medical Technology and Practice Patterns Institute, Inc., 4733 Bethesda Avenue, Suite 510, Bethesda, MD 20814, USA. dcott@mtppi.org
authors.forename: Dennis J
authors.initials: DJ
authors.lastname: Cotter
authors.forename: Kevin
authors.initials: K
authors.lastname: Stefanik
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Mae
authors.initials: M
authors.lastname: Thamer
authors.forename: Daniel
authors.initials: D
authors.lastname: Scharfstein
authors.forename: James
authors.initials: J
authors.lastname: Kaufman
mesh_terms: D004305:Dose-Response Relationship, Drug; D000068817:Epoetin Alfa; D004921:Erythropoietin / Q000008:administration & dosage* / Q000627:therapeutic use; D006397:Hematinics / Q000008:administration & dosage* / Q000627:therapeutic use; D006400:Hematocrit; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood / Q000401:mortality / Q000628:therapy*; D011446:Prospective Studies; D011994:Recombinant Proteins; D012044:Regression Analysis; D006435:Renal Dialysis; D015996:Survival Rate
chemical_list: D006397:Hematinics; D011994:Recombinant Proteins; D004921:Erythropoietin; D000068817:Epoetin Alfa