title: Relationship of serum cystatin C to peritoneal and renal clearance measures in peritoneal dialysis: a cross-sectional study.
abstract: BACKGROUND
  Clinical management of peritoneal dialysis patients includes assessments of peritoneal and renal clearances of the low-molecular-weight endogenous solutes creatinine and urea. Cystatin C is a low-molecular-weight protein used as a glomerular filtration rate marker. We investigated whether serum cystatin C concentration is related to peritoneal and renal clearances of creatinine and urea.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  119 patients undergoing peritoneal dialysis in a single dialysis unit.
  
  
  METHODS
  Peritoneal, renal, and total clearance of urea as Kt/V(urea) and creatinine as weekly creatinine clearance (C(Cr)). Residual renal function (RRF) as the average of renal clearances of urea and creatinine.
  
  
  METHODS
  Serum concentrations of cystatin C measured by using a particle-enhanced nephelometric immunoassay.
  
  
  RESULTS
  Serum cystatin C concentration was related inversely to RRF (Spearman rank correlation coefficient [r(s)] = -0.65; P < 0.001), total weekly C(Cr) (r(s) = -0.52; P < 0.001), and total Kt/V(urea) (r(s) = -0.23; P = 0.01). In a multiple regression model, weight, normalized protein catabolic rate, and RRF had independent effects on serum cystatin C concentrations. Additional multiple regression models showed that only the renal components of Kt/V(urea) and weekly C(Cr) contributed to serum cystatin C concentrations.
  
  
  CONCLUSIONS
  Absence of reference GFR method.
  
  
  CONCLUSIONS
  Serum cystatin C concentrations reflect predominantly renal, not peritoneal, clearance. Serum cystatin C measurement may be a simple and practical alternative to measurement of RRF.
authors.affiliation: Department of Renal Medicine, East Kent Hospitals NHS Trust, Kent and Canterbury Hospital, Canterbury, Kent, UK.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Delaney
authors.forename: Paul E
authors.initials: PE
authors.lastname: Stevens
authors.forename: Mohammed
authors.initials: M
authors.lastname: Al Hasani
authors.forename: Helen J
authors.initials: HJ
authors.lastname: Stowe
authors.forename: Caroline
authors.initials: C
authors.lastname: Judge
authors.forename: Edmund J
authors.initials: EJ
authors.lastname: Lamb
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001202:Ascitic Fluid / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D015331:Cohort Studies; D003404:Creatinine / Q000378:metabolism* / Q000652:urine; D003430:Cross-Sectional Studies; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D010530:Peritoneal Dialysis; D011237:Predictive Value of Tests; D012107:Research Design; D014508:Urea / Q000378:metabolism* / Q000652:urine
chemical_list: D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D014508:Urea; D003404:Creatinine