title: Interdialytic creatinine change versus predialysis creatinine as indicators of nutritional status in maintenance hemodialysis.
abstract: BACKGROUND
  Protein-energy wasting is common in patients on maintenance hemodialysis and is strongly associated with poor quality of life and mortality. However, clinical assessment of protein-energy wasting remains difficult. Predialysis creatinine levels are associated with mortality risk but may be influenced by both muscle mass and dialysis dose. This might be overcome by examining the rate of rise in creatinine between dialysis sessions.
  
  
  METHODS
  We conducted an observational cohort study among 81 patients on maintenance hemodialysis at our Veterans Affairs unit. Predialysis serum creatinine and change in serum creatinine between midweek dialysis sessions served as the predictor variables of interest and clinically available proxies of nutritional status and time to mortality served as the outcome variables. Linear regression and Cox proportional hazards models evaluated relationships, respectively.
  
  
  RESULTS
  The mean age of the study participants was 63 ± 10 years, 77 (95%) were male, mean body mass index was 27 ± 6 kg/m(2) and 69% had diabetes. Median follow-up time was 13 months, during which 12 patients (15%) died. Interdialytic change in serum creatinine showed a strong direct correlation with predialysis serum creatinine (R = 0.96). Higher levels of both markers were associated with younger age, less residual urine volume and higher serum albumin, serum phosphorus and normalized protein catabolic rate (P < 0.05 for all). Both markers were approximately equally strongly associated with mortality. For example, compared to the highest predialysis creatinine tertile, participants in the lowest tertile (<6 mg/dL) had 5.5-fold [95% confidence interval (CI) 1.1, 26.6] higher risk of death. Similarly, participants in the lowest tertile of interdialytic change in creatinine (change <3.7 mg/dL/48 h), had 5.0-fold (95% CI 1.0, 24.4) higher death risk.
  
  
  CONCLUSIONS
  Predialysis creatinine and interdialytic change in creatinine are both strongly associated with proxies of nutritional status and mortality in hemodialysis patients and are highly correlated. Interdialytic change in creatinine provided little additional information about nutritional status or mortality risk above and beyond predialysis creatinine levels alone.
authors.affiliation: Department of Medicine, University of California San Diego, San Diego, CA, USA.
authors.forename: Carl P
authors.initials: CP
authors.lastname: Walther
authors.forename: Caitlin Wise
authors.initials: CW
authors.lastname: Carter
authors.forename: Chai L
authors.initials: CL
authors.lastname: Low
authors.forename: Peter
authors.initials: P
authors.lastname: Williams
authors.forename: Dena E
authors.initials: DE
authors.lastname: Rifkin
authors.forename: Robert W
authors.initials: RW
authors.lastname: Steiner
authors.forename: Joachim H
authors.initials: JH
authors.lastname: Ix
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood; D015992:Body Mass Index; D015331:Cohort Studies; D003404:Creatinine / Q000097:blood*; D005260:Female; D006787:Hospitals, Veterans; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000628:therapy; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009751:Nutritional Requirements; D009752:Nutritional Status; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D011502:Protein-Energy Malnutrition / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology; D006435:Renal Dialysis / Q000009:adverse effects* / Q000379:methods; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D013997:Time Factors
chemical_list: D015415:Biomarkers; D003404:Creatinine