title: The utility of the growth hormone (GH) releasing hormone-arginine test for diagnosing GH deficiency in adults with childhood acute lymphoblastic leukemia treated with cranial irradiation.
abstract: BACKGROUND
  The insulin tolerance test (ITT) is the current standard diagnostic test for the diagnosis of adult GH deficiency (GHD), but alternative tests, such as the GHRH-arginine test, have been proposed.
  
  
  OBJECTIVE
  We investigated the sensitivity and specificity of the GHRH-arginine test using ITT as the gold standard in diagnosing GHD in a group of young adults treated with cranial irradiation (CRT) for childhood acute lymphoblastic leukemia (ALL). We estimated the positive and negative predictive values of the GHRH-arginine test among patients as well as a number of individual characteristics and therapy-related factors during both the GHRH-arginine test and ITT.
  
  
  METHODS
  Forty-three young adults, treated for childhood ALL with 18-30 Gy CRT and chemotherapy, were studied, and comparison was made with matched controls.
  
  
  CONCLUSIONS
  We evaluated four different cutoff levels for GHD in the GHRH-arginine test: 5, 7.5, 9, and 16.5 microg/liter. Using 7.5 microg/liter as the cutoff yielded high specificity (94%), but at the same time the sensitivity was only 66%, which leads to a low negative predictive value (27%). In contrast, a failed GH response to the GHRH-arginine test accurately reflects the presence of radiation-induced GHD, illustrated by a high positive predictive value (95% at 7.5 microg/liter). Only age at CRT and body mass index remained significant predictors of the peak GH during the GHRH-arginine test. Because a high proportion of GHD patients show a normal response to the GHRH-arginine test, it cannot be used reliably to exclude GHD in these patients. Complementary ITT is also warranted to confirm GHD in obese patients.
authors.affiliation: Center for Clinical Research, Lund University Hospital, SE-221 85 Lund, Sweden.
authors.forename: Jonas
authors.initials: J
authors.lastname: Björk
authors.forename: Katarina
authors.initials: K
authors.lastname: Link
authors.forename: Eva Marie
authors.initials: EM
authors.lastname: Erfurth
mesh_terms: D000328:Adult; D000367:Age Factors; D001120:Arginine; D016371:Cranial Irradiation; D005260:Female; D013007:Growth Hormone-Releasing Hormone; D019382:Human Growth Hormone / Q000172:deficiency*; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D008297:Male; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000378:metabolism / Q000532:radiotherapy*; D012680:Sensitivity and Specificity
chemical_list: D007328:Insulin; D019382:Human Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D001120:Arginine