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.
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.
Björk
Jonas
J
Center for Clinical Research, Lund University Hospital, SE-221 85 Lund, Sweden.
Link
Katarina
K
Erfurth
Eva Marie
EM
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
D007328:Insulin; D019382:Human Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D001120:Arginine