title: Performance of the Japanese glomerular filtration rate equation based on standardized serum cystatin C in potential kidney donors.
abstract: BACKGROUND
  It was reported that the glomerula filtration rate (GFR) equation based on serum creatinine underestimated the GFR in potential kidney donors. Recently, the Japanese GFR equation based on standardized serum cystatin C was reported. Therefore, we assessed the performance of the equation in potential kidney donors.
  
  
  METHODS
  Forty-five potential kidney donors from 2 hospitals were included. GFR was measured (mGFR) using inulin renal clearance. Serum creatinine was measured using the enzymatic method. Serum cystatin C was measured using a nephelometric immunoassay (Siemens) and calibrated to the standardized value traceable to ERM-DA471/IFCC using an equation reported previously. The estimated GFR (eGFR) was calculated using the Japanese GFR equation based on serum creatinine (eGFRcreat) and the Japanese GFR equation based on serum cystatin C (eGFRcys). Bias (mGFR - eGFR) and accuracy (P30) of the equations were evaluated.
  
  
  RESULTS
  Inulin clearance, eGFRcreat, and eGFRcys were 91.0 ± 18.2, 78.5 ± 18.8, and 93.3 ± 16.3 mL/min/1.73 m(2), respectively. Bias of eGFRcreat was 12.4 ± 15.8 mL/min/1.73 m(2) and significantly different from zero, indicating underestimation of GFR. Bias of eGFRcys was -2.3 ± 16.3 mL/min/1.73 m(2) and was not significantly different from zero, suggesting better performance. But, the precision (standard deviation [SD] of bias) and accuracy (P30: Percentage of participants with eGFR within 30% of mGFR) of eGFRcys were not better compared with eGFRcreat. Accuracies (P30) of eGFRcreat and eGFRcys were 87% (95% confidence interval [CI], 74-94) and 82% (95% CI, 69-91), respectively.
  
  
  CONCLUSIONS
  Bias of eGFRcys was better compared with eGFRcreat. But, the precision (SD of bias) and accuracy of eGFRcys were not superior compared with eGFRcreat in potential kidney donors.
authors.affiliation: Department of Functional Diagnostic Science, Osaka University Graduate School of Medicine, Osaka, Japan. Electronic address: horio@sahs.med.osaka-u.ac.jp.
authors.forename: M
authors.initials: M
authors.lastname: Horio
authors.affiliation: Department of Nephrology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Yasuda
authors.affiliation: Departments of Geriatric Medicine and Nephrology, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Kaimori
authors.affiliation: Department of Specific Organ Regulation, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Ichimaru
authors.affiliation: Department of Specific Organ Regulation, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Kakuta
authors.affiliation: Departments of Geriatric Medicine and Nephrology, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Isaka
authors.affiliation: Department of Nephrology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Matsuo
authors.affiliation: Department of Advanced Technology for Transplantation, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Takahara
mesh_terms: D000368:Aged; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007564:Japan; D016030:Kidney Transplantation; D008297:Male; D008875:Middle Aged; D014019:Tissue Donors
chemical_list: D055316:Cystatin C