Combined growth hormone stimulation testing: Could the tests be shortened?

Introduction: Growth hormone stimulation tests (GHST) remain the cornerstone for diagnosing growth hormone deficiency (GHD), yet they can be lengthy and costly. We aimed to examine whether the combined clonidine and glucagon stimulation test (CGST) and l-dopa and glucagon stimulation test (LDGST) can be shortened without compromising the test's specificity.

Material And Methods: We retrospectively analyzed the baseline characteristics, auxological and laboratory data of children with short stature who had undergone a CGST and an LDGST for GHD. We compared the diagnostic accuracy for the standard test and shortened test, eliminating time points of 0 and 210 min.

Results: We reviewed 830 charts (8.17 ± 2.92 years old; 56.27% males), with 431 (57.0%) children in the CGST group, and 38 (51.35%) in the LDGST group who tested negative for GHD. The peak and maximum GH levels occurred at the 60-min time point for both the CGST and LDGST. Eliminating the 0-min time point was the only time that did not affect the specificity of the CGST, with a false-positive rate of 2 (2.99%), specificity of 0.99 (0.99-0.99), and p value of 0.25. Eliminating the 0- and 210-min time points did not affect the specificity of the LDGST, with a false-positive rate of 2 (5.26%), specificity of 0.95 (0.95-0.95), and p value of 0.24.

Conclusions: We concluded that 0-min time point could be eliminated without compromising the combined GHST diagnostic value, thus resulting in cost reduction. Larger studies are needed for the combined LDGST to explore whether the 30- and 210-min time points could be eliminated, thus resulting in cost and time savings.