No advantage of the new combined octreotide-GHRH test over established GH-stimulation tests in the diagnosis of growth hormone deficiency (GHD) in adults

OBJECTIVE To evaluate the sensitivity and specificity of a combined octreot ide (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 diagnos is of GHD in adults it is difficult to define the relative merits of differ ent tests in patients with structural pituitary disease. We have addressed this by grouping patients according to the degree of concordance between th ree established tests (insulin (IHT), arginine (ARG) and GHRH stimulation t est (GHRH)) and serum IGF-I levels and have subsequently analysed the frequ ency destribution of test results across defined groups: group 1, with comp lete 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 wh ich were compared with IHT, ARG and GHRH. MEASUREMENTS Five hours after an octreotide injection GHRH was given intrav enously and GH measured. RESULTS ARG had the highest sensitivity (Se = 100%) and specificity (Sp = 1 00%) of the tests used, The IHT also diagnosed GHD with precision but showe d false positive as well as false negative results (Se = 90%, Sp = 100%), S e 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 establis hed tests and that the octreotide-GHRH test does not have any advantages fo r diagnosing GHD in adults. IGF-1 levels can be used as a screening test on ly. The arginine test was the best conventional test in our study.