title: Which equations should and which should not be employed in calculating eGFR in children?
abstract: OBJECTIVE
  We assessed the reliability of calculating eGFR in children as compared to the iohexol disappearance test (GFR-I), which was performed 417 times in 353 children aged 2 and more.
  
  
  METHODS
  eGFR was estimated with equations based on serum creatinine: Schwartz (1: eGFR-Scr), Cockroft-Gault (2: eGFR-CG) and MDRD (3: eGFR-MDRD), and on creatinine clearance (4: eGFR-U), or relying on serum cystatin C: Hoeck (5: eGFR-H), Bokenkamp (6: eGFR-B) and Filler (7: eGFR-F), and on the three Schwartz markers (8: eGFR-S3M). Mean relative error (RE), correlation (R), Bland-Altman analysis and accuracy of GFR-I were studied in all patients and in subgroups: at GFR<60ml/min/1.73m(2); in children aged ≤12 and >12.
  
  
  RESULTS
  The results by eGFR-Scr, eGFR-S3M demonstrated no statistical difference to GFR-I at GFR<60ml/min/1.73m(2), but underestimated eGFR at higher filtration values by 11.6±15.1% and 19.1±16.4, respectively (p<0.0000). The eGFR-B, eGFR-F and eGFR-MDRD equations illustrated important overestimation of reference GFR results (RE: 84±44.2%; 29.5±27.9%, 35.6±62%; p<0.0000 for all). The MDRD and C-G formulas showed statistically better consistency in children aged >12. A good agreement was achieved by the eGFR-H equation (5.1±21.9%; p<0.0000; R=0.78).
  
  
  CONCLUSIONS
  (1) Schwartz equations show a good conformity at GFR<60ml/min/1.73m(2), but underestimate the results at higher GFR values. (2) The Bokenkamp equation with original coefficient should not be employed in children. (3) The use of the Hoeck formula in all children and C-G and MDRD formula in children aged >12 is possible. (4) The error of eGFR calculations increases at higher GFR values.
authors.affiliation: Department of Pediatric Nephrology, Jagiellonian University Medical College, Cracow, Poland. Electronic address: katarzyna.zachwieja@gmail.com.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Zachwieja
authors.affiliation: Department of Electronics, Faculty of Computer Science, Electronics and Telecommunications, AGH University of Science and Technology, Cracow, Poland.
authors.forename: Przemysław
authors.initials: P
authors.lastname: Korohoda
authors.affiliation: Department of Pediatric Nephrology, Children's University Hospital of Cracow, Cracow, Poland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Kwinta-Rybicka
authors.affiliation: Department of Pediatric Nephrology, Jagiellonian University Medical College, Cracow, Poland.
authors.forename: Monika
authors.initials: M
authors.lastname: Miklaszewska
authors.affiliation: Department of Pediatric Nephrology, Jagiellonian University Medical College, Cracow, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Moczulska
authors.affiliation: Clinical Biochemistry Department, Jagiellonian University Medical College, Cracow, Poland.
authors.forename: Jolanta
authors.initials: J
authors.lastname: Bugajska
authors.affiliation: Clinical Biochemistry Department, Jagiellonian University Medical College, Cracow, Poland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Berska
authors.affiliation: Department of Pediatric Nephrology, Jagiellonian University Medical College, Cracow, Poland.
authors.forename: Dorota
authors.initials: D
authors.lastname: Drożdż
authors.affiliation: Department of Pediatric Nephrology, Jagiellonian University Medical College, Cracow, Poland.
authors.forename: Jacek A
authors.initials: JA
authors.lastname: Pietrzyk
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D003404:Creatinine / Q000097:blood; D055316:Cystatin C / Q000097:blood; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007472:Iohexol / Q000378:metabolism; D007677:Kidney Function Tests; D008297:Male; D015203:Reproducibility of Results
chemical_list: D055316:Cystatin C; D007472:Iohexol; D003404:Creatinine
keywords: Children; Creatinine; Cystatin C; Iohexol; eGFR calculation