title: Estimation of residual glomerular filtration rate in peritoneal dialysis patients using cystatin C: comparison with 51Cr-EDTA clearance.
abstract: BACKGROUND
  Measuring glomerular filtration rate (GFR) is an important assessment in peritoneal dialysis patients. In clinical practice, it is commonly measured by calculating the mean of the urinary clearance of urea and creatinine (GFR(UrCl)) but this process is time consuming and unreliable. We wished to compare several estimates of GFR including residual GFR estimated from cystatin C (GFR(CysC)) using a published equation (Hoek), GFR(UrCl) and (51)Cr-ethylenediaminetetraacetic acid (EDTA) clearance, in peritoneal dialysis patients.
  
  
  METHODS
  GFR(CysC), GFR(UrCl) and (51)Cr-EDTA clearance were measured in 28 patients undergoing peritoneal dialysis in a single dialysis unit.
  
  
  RESULTS
  GFR(CysC) was related to GFR(UrCl) (Spearman's rank correlation coefficient r(s) = 0.44; P = 0.0185) and to (51)Cr-EDTA clearance (r(s) = 0.48; P = 0.0099). GFR(CysC) values were significantly (P = 0.0077) lower than (51)Cr-EDTA clearance results (mean bias -19.7%). However, GFR(CysC) did not differ significantly (P > 0.05) from GFR(UrCl).
  
  
  CONCLUSIONS
  GFR(CysC) is related to GFR(UrCl) but has a significant negative bias against (51)Cr-EDTA. Given the known limitations of (51)Cr-EDTA in estimating GFR in renal failure, this study provides additional validation suggesting that cystatin C-estimated rGFR (GFR(CysC)) gives a reasonable estimation of GFR without the clinical problems associated with 24 h urine collections.
authors: Department of Clinical Biochemistry, East Kent Hospitals University NHS Foundation Trust, Canterbury, Kent, UK. joannecarter@nhs.net
authors: Joanne L
authors: JL
authors: Carter
authors: Catherine E
authors: CE
authors: Lane
authors: Stanley L
authors: SL
authors: Fan
authors: Edmund J
authors: EJ
authors: Lamb
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood / Q000652:urine; D002860:Chromium Radioisotopes; D003404:Creatinine / Q000097:blood / Q000652:urine; D055316:Cystatin C / Q000097:blood*; D004492:Edetic Acid / Q000378:metabolism*; D005260:Female; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000503:physiopathology*; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D010530:Peritoneal Dialysis; D011379:Prognosis; D018709:Statistics, Nonparametric; D014508:Urea / Q000097:blood / Q000652:urine; D059349:Urine Specimen Collection; D055815:Young Adult
chemical_list: D015415:Biomarkers; D002860:Chromium Radioisotopes; D055316:Cystatin C; D014508:Urea; D004492:Edetic Acid; D003404:Creatinine