title: Compensating for the influence of total serum protein in the Schwartz formula.
abstract: BACKGROUND
  The Schwartz 2009 creatinine-based revised formula is the only pediatric GFR estimating formula, which is compatible with the recent global creatinine standardization. This formula is only applicable if enzymatic creatinine methods are used. We propose an equation, taking into account the relative bias caused by serum proteins to use Jaffe based creatinine data for GFR estimation.
  
  
  METHODS
  In a cohort study of 100 pediatric patients, serum creatinine was measured using a kinetic rate-blanked Jaffe assay (modified kinetic alkaline picrate method), a kinetic rate-blanked Jaffe compensated assay for reactive proteins and an enzymatic assay (creatinine plus method). Serum total protein, albumin, urea, uric acid and total bilirubin were measured with the use of commercial agents.
  
  
  RESULTS
  The difference in serum creatinine between the enzymatic method and the compensated Jaffe method was mainly dependent on the total protein concentration in serum (r(2)=0.61, p<0.001). After applying the proposed protein correction, corrected compensated Jaffe results and creatinine clearance values became interchangeable with enzymatic serum creatinine results (r(2)=0.99, p<0.001; Deming regression: slope: 0.9787, intercept: -0.351) and with the newly proposed Schwartz formula, respectively (r(2)=0.99, p<0.001; Deming regression: slope 1.004, intercept: 2.16).
  
  
  CONCLUSIONS
  In this study, we demonstrated the usability of the alkaline picrate method in the Schwartz formula, taking into account the relative bias caused by serum proteins.
authors.affiliation: Department of Nephrology, Ghent University Hospital, Ghent, Belgium.
authors.forename: Marijn M
authors.initials: MM
authors.lastname: Speeckaert
authors.forename: Birgitte
authors.initials: B
authors.lastname: Wuyts
authors.forename: Veronique
authors.initials: V
authors.lastname: Stove
authors.forename: Johan Vande
authors.initials: JV
authors.lastname: Walle
authors.forename: Joris R
authors.initials: JR
authors.lastname: Delanghe
mesh_terms: D000293:Adolescent; D001798:Blood Proteins / Q000737:chemistry* / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003404:Creatinine / Q000097:blood; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology; D006801:Humans; D008297:Male; D009942:Organometallic Compounds / Q000737:chemistry*
chemical_list: D001798:Blood Proteins; D009942:Organometallic Compounds; C532427:Schwartz reagent; D003404:Creatinine