title: Dialysis dose scaled to body surface area and size-adjusted, sex-specific patient mortality.
abstract: OBJECTIVE
  When hemodialysis dose is scaled to body water (V), women typically receive a greater dose than men, but their survival is not better given a similar dose. This study sought to determine whether rescaling dose to body surface area (SA) might reveal different associations among dose, sex, and mortality.
  
  
  METHODS
  Single-pool Kt/V (spKt/V), equilibrated Kt/V, and standard Kt/V (stdKt/V) were computed using urea kinetic modeling on a prevalent cohort of 7229 patients undergoing thrice-weekly hemodialysis. Data were obtained from the Centers for Medicare & Medicaid Services 2008 ESRD Clinical Performance Measures Project. SA-normalized stdKt/V (SAN-stdKt/V) was calculated as stdKt/V × ratio of anthropometric volume to SA/17.5. Patients were grouped into sex-specific dose quintiles (reference: quintile 1 for men). Adjusted hazard ratios (HRs) for 1-year mortality were calculated using Cox regression.
  
  
  RESULTS
  spKt/V was higher in women (1.7 ± 0.3) than in men (1.5 ± 0.2; P<0.001), but SAN-stdKt/V was lower (women: 2.3 ± 0.2; men: 2.5 ± 0.3; P<0.001). For both sexes, mortality decreased as spKt/V increased, until spKt/V was 1.6-1.7 (quintile 4 for men: HR, 0.62; quintile 3 for women: HR, 0.64); no benefit was observed with higher spKt/V. HR for mortality decreased further at higher SAN-stdKt/V in both sexes (quintile 5 for men: HR, 0.69; quintile 5 for women: HR, 0.60).
  
  
  CONCLUSIONS
  SA-based dialysis dose results in dose-mortality relationships substantially different from those with volume-based dosing. SAN-stdKt/V analyses suggest women may be relatively underdosed when treated by V-based dosing. SAN-stdKt/V as a measure for dialysis dose may warrant further study.
authors.affiliation: Arbor Research Collaborative for Health, Ann Arbor, Michigan, USA. sylvia.ramirez@arborresearch.org
authors.forename: Sylvia Paz B
authors.initials: SP
authors.lastname: Ramirez
authors.forename: Alissa
authors.initials: A
authors.lastname: Kapke
authors.forename: Friedrich K
authors.initials: FK
authors.lastname: Port
authors.forename: Robert A
authors.initials: RA
authors.lastname: Wolfe
authors.forename: Rajiv
authors.initials: R
authors.lastname: Saran
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Pearson
authors.forename: Richard A
authors.initials: RA
authors.lastname: Hirth
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Messana
authors.forename: John T
authors.initials: JT
authors.lastname: Daugirdas
mesh_terms: D000368:Aged; D001830:Body Surface Area; D016009:Chi-Square Distribution; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood / Q000401:mortality* / Q000628:therapy*; D008875:Middle Aged; D016016:Proportional Hazards Models; D006435:Renal Dialysis / Q000379:methods*; D012737:Sex Factors; D018709:Statistics, Nonparametric; D013997:Time Factors; D014508:Urea / Q000097:blood
chemical_list: D014508:Urea