title: A novel equation to estimate glomerular filtration rate using beta-trace protein.
abstract: BACKGROUND
  Beta-trace protein (BTP) is a low molecular weight glycoprotein that is a more sensitive marker of glomerular filtration rate (GFR) than serum creatinine. The utility of BTP has been limited by the lack of an equation to translate BTP into an estimate of GFR. The objectives of this study were to develop a BTP-based GFR estimation equation.
  
  
  METHODS
  We measured BTP and GFR by (99m)technetium-diethylenetriaminepentaacetic acid in 163 stable adult renal transplant recipients. Stepwise multiple regression models were created to predict GFR corrected for body surface area. The following variables were considered for entry into the model: BTP, urea, sex, albumin, creatinine, age, and race.
  
  
  RESULTS
  BTP alone accounted for 75.6% of variability in GFR. The model that included all the predictor variables had the largest coefficient of determination (R(2)) at 0.821. The model with only BTP, urea, and sex had only a slightly lower R(2) of 0.81 and yielded the following equation: GFR mL . min(-1) . (1.73 m(2))(-1) = 112.1 x BTP(-0.662) x Urea(-0.280) x (0.88 if female). A 2nd equation (R(2) = 0.79) using creatinine instead of urea was also developed: GFR mL . min(-1) . (1.73 m(2))(-1) = 1.678 x BTP(-0.758) x creatinine(-0.204) x (0.871 if female).
  
  
  CONCLUSIONS
  We have shown that BTP can be used in a simple equation to estimate GFR. Further study is needed in other populations to determine accuracy and clinical utility of this equation.
authors.affiliation: Division of Nephrology, Department of Medicine, Queen's University, Kingston, Canada.
authors.forename: Christine A
authors.initials: CA
authors.lastname: White
authors.forename: Ayub
authors.initials: A
authors.lastname: Akbari
authors.forename: Steve
authors.initials: S
authors.lastname: Doucette
authors.forename: Dean
authors.initials: D
authors.lastname: Fergusson
authors.forename: Naser
authors.initials: N
authors.lastname: Hussain
authors.forename: Laurent
authors.initials: L
authors.lastname: Dinh
authors.forename: Guido
authors.initials: G
authors.lastname: Filler
authors.forename: Nathalie
authors.initials: N
authors.lastname: Lepage
authors.forename: Greg A
authors.initials: GA
authors.lastname: Knoll
mesh_terms: D000328:Adult; D000465:Algorithms; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D019746:Intramolecular Oxidoreductases / Q000097:blood*; D016030:Kidney Transplantation; D054834:Lipocalins / Q000097:blood*; D008297:Male; D012372:ROC Curve; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012044:Regression Analysis; D016284:Technetium Tc 99m Pentetate / Q000493:pharmacokinetics
chemical_list: D054834:Lipocalins; D019275:Radiopharmaceuticals; D019746:Intramolecular Oxidoreductases; C022466:prostaglandin R2 D-isomerase; D016284:Technetium Tc 99m Pentetate