title: Beta-trace protein, cystatin C, beta(2)-microglobulin, and creatinine compared for detecting impaired glomerular filtration rates in children.
abstract: BACKGROUND
  Because of the limitations of serum creatinine as a marker of glomerular filtration rate (GFR) in children, we assessed the diagnostic accuracy of the novel marker beta-trace protein (BTP) in comparison with cystatin C (Cys-C), beta(2)-microglobulin (beta(2)-MG), and creatinine as conventional indicators of reduced GFR.
  
  
  METHODS
  We obtained serum samples from 225 children (age range, 0.2-18 years) with various renal pathologies who were referred for nuclear medicine clearance investigations (technetium-diethylenetriamine pentaacetic acid or chromium-EDTA). We measured Cys-C, BTP (nephelometric tests; Dade Behring), beta(2)-MG (Tinaquant; Roche), and creatinine (enzymatic assay; Creatinine-PAP; Roche).
  
  
  RESULTS
  Seventy-five children had reduced GFR (<90 mL x min(-1) x 1.73 m(-2)). One hundred fifty children (independent of gender and age) with values >90 mL x min(-1) x 1.73 m(-2) comprised the control group with gaussian distributions of BTP and Cys-C concentrations. The upper reference limits (97.5 percentile) were 1.01 mg/L for BTP and 1.20 mg/L for Cys-C. The correlations of nuclear medicine clearance with the reciprocals of BTP, Cys-C, and the Schwartz GFR estimate were significantly higher (r = 0.653, 0.765, and 0.706, respectively; P <0.05) than with the reciprocal of creatinine or beta(2)-MG (r = 0.500 and 0.557, respectively). ROC analysis showed a significantly higher diagnostic accuracy of BTP, Cys-C, and the GFR estimate for the detection of impaired GFR than serum creatinine (P <0.05). Compared to creatinine, BTP increased the diagnostic sensitivity by approximately 30%, but it was not more sensitive than Cys-C or the Schwartz GFR estimate.
  
  
  CONCLUSIONS
  BTP is superior to serum creatinine and an alternative for Cys-C to detect mildly reduced GFR in children, but it is not better than the Schwartz GFR estimate.
authors.affiliation: Departments of Pediatrics, Children's Hospital of Eastern Ontario, Ottawa, Ontario, K1H 8L1 Canada.
authors.forename: Guido
authors.initials: G
authors.lastname: Filler
authors.forename: Friedrich
authors.initials: F
authors.lastname: Priem
authors.forename: Nathalie
authors.initials: N
authors.lastname: Lepage
authors.forename: Pranav
authors.initials: P
authors.lastname: Sinha
authors.forename: Ilka
authors.initials: I
authors.lastname: Vollmer
authors.forename: Heather
authors.initials: H
authors.lastname: Clark
authors.forename: Erin
authors.initials: E
authors.lastname: Keely
authors.forename: Mary
authors.initials: M
authors.lastname: Matzinger
authors.forename: Ayub
authors.initials: A
authors.lastname: Akbari
authors.forename: Harald
authors.initials: H
authors.lastname: Althaus
authors.forename: Klaus
authors.initials: K
authors.lastname: Jung
mesh_terms: D000293:Adolescent; D015415:Biomarkers / Q000097:blood; D002648:Child; D002675:Child, Preschool; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007223:Infant; D019746:Intramolecular Oxidoreductases / Q000097:blood*; D007674:Kidney Diseases / Q000175:diagnosis* / Q000503:physiopathology; D054834:Lipocalins; D008297:Male; D012016:Reference Values; D001613:beta 2-Microglobulin / Q000097:blood*
chemical_list: D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D054834:Lipocalins; D001613:beta 2-Microglobulin; D003404:Creatinine; D019746:Intramolecular Oxidoreductases; C022466:prostaglandin R2 D-isomerase