The shortened combined clonidine and arginine test for growth hormone deficiency is practical and specific: a diagnostic accuracy study

Background: The growth hormone (GH) stimulation-protocols for clonidine and arginine tests are non-standardized and can be lengthy. We examined the specificity of both tests using a shorter duration of timed samples: 90 min for clonidine and 60 min for arginine. Methods: We retrospectively studied all children who had GH stimulation with clonidine and arginine to test for GH deficiency (GHD). We compared the diagnostic accuracy of both reference and new shortened test (index). Results: We reviewed 243 charts (11.4 +/- 4.1 years old; 74.5% males). The combined reference test was performed on 159 children, 29 (18.3%) tested positive for GHD on the combined index test, Kappa 0.98, false positive rate 1 (0.8%), specificity 0.99, 95th CI (0.96-1), and p = 1.0. The specificity of both the clonidine and arginine single index tests was 0.98%. Conclusions: The shortened clonidine and arginine stimulation index tests have good specificity. This is a viable option for testing children for GHD.