Objective: To evaluate the sensitivity and specificity of a combined octreotide (SMS)-GHRH test we compared it with established GH stimulation tests in the diagnosis of growth hormone deficiency (GHD) in adults.
Design: Because there is no universally agreed gold standard for the diagnosis of GHD in adults it is difficult to define the relative merits of different tests in patients with structural pituitary disease. We have addressed this by grouping patients according to the degree of concordance between three established tests (insulin (IHT), arginine (ARG) and GHRH stimulation test (GHRH)) and serum IGF-I levels and have subsequently analysed the frequency destribution of test results across defined groups: group 1, with complete GHD in all tests, group 2, with differences between tests with regard to the diagnosis of GHD and group 3, with normal GH response in all tests. The patients also underwent a new combined SMS-GHRH test, the results of which were compared with IHT, ARG and GHRH.
Measurements: Five hours after an octreotide injection GHRH was given intravenously and GH measured.
Results: ARG had the highest sensitivity (Se = 100%) and specificity (Sp = 100%) of the tests used. The IHT also diagnosed GHD with precision but showed false positive as well as false negative results (Se = 90%, Sp = 100%). Se and Sp of GHRH were lower than those of IHT and ARG (Se = 100%, Sp = 89%). The SMS-GHRH worked well and was superior to GHRH but had less precision than IHT and ARG (Se = 88%, Sp = 100%).
Conclusion: We conclude that there is discordance between the three established tests and that the octreotide-GHRH test does not have any advantages for diagnosing GHD in adults. IGF-I levels can be used as a screening test only. The arginine test was the best conventional test in our study.