title: Central reassessment of GH concentrations measured at local treatment centers in children with impaired growth: consequences for patient management.
abstract: OBJECTIVE
  GH deficiency is diagnosed in children if serum GH fails to rise above a predefined cutoff value in response to at least two stimuli. Diagnostic decisions based on this testing are highly variable between centers and depend on the GH assays used. Considering the large spectrum of commercially available GH assays, we wanted to evaluate the agreement between assays, and to test whether assay-related variability of diagnostic decisions could be reduced by reassessment of peak GH concentrations in a reference center.
  
  
  METHODS
  We reanalysed 699 peak GH serum samples obtained after GH testing of 382 children and adolescents from 19 centers using three reference assays and compared these results with those obtained with the local assays. A subgroup of 132 patients tested with the combination of insulin hypoglycemia test and arginine test was evaluated for changes in the assignment to the diagnostic group of GH deficiency.
  
  
  RESULTS
  The mean difference between methods ranged from 5.4 to 10.3 mU/l, slopes of the regression lines from 1.28 to 1.65. Significant non-linearity was detected in five of six assay comparisons, indicating that most assay results cannot be interconverted by the use of a factor. Overall agreement between reference and local assays was only moderate. Significant changes in diagnostic assignment occurred when different assays were used on the same patient (P<0.0001-P<0.0023). Based on GH remeasurement by one reference assay, 36 of 132 patients were categorized differently, with 35 patients changing into the GH-deficient group. Similar findings were obtained with the other reference assays.
  
  
  CONCLUSIONS
  To decrease variability in GH testing related to assays and cutoff values, we recommend nationwide reassessment of GH peak sera in reference centers. Decisions to treat GH deficiency should incorporate the reference center results.
authors.affiliation: Department of Pediatric Hematology/Oncology and Endocrinology, University Children's Hospital, Essen, Germany. berthold.hauffa@uni-essen.de
authors.forename: Berthold P
authors.initials: BP
authors.lastname: Hauffa
authors.forename: Nils
authors.initials: N
authors.lastname: Lehmann
authors.forename: Markus
authors.initials: M
authors.lastname: Bettendorf
authors.forename: Otto
authors.initials: O
authors.lastname: Mehls
authors.forename: Helmuth-Günther
authors.initials: HG
authors.lastname: Dörr
authors.forename: Carl-Joachim
authors.initials: CJ
authors.lastname: Partsch
authors.forename: Hans P
authors.initials: HP
authors.lastname: Schwarz
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Stahnke
authors.forename: Heinz
authors.initials: H
authors.lastname: Steinkamp
authors.forename: Elfriede
authors.initials: E
authors.lastname: Said
authors.forename: Sabine
authors.initials: S
authors.lastname: Sander
authors.forename: Michael B
authors.initials: MB
authors.lastname: Ranke
mesh_terms: D000293:Adolescent; D002648:Child; D005260:Female; D006130:Growth Disorders / Q000097:blood* / Q000175:diagnosis; D019382:Human Growth Hormone / Q000097:blood / Q000172:deficiency*; D006801:Humans; D008297:Male; D011933:Reagent Kits, Diagnostic; D012044:Regression Analysis; D015203:Reproducibility of Results
chemical_list: D011933:Reagent Kits, Diagnostic; D019382:Human Growth Hormone