Shortening L-DOPA testing time in the diagnosis of growth hormone deficiency: is it possible?

Abstract Introduction: Growth hormone deficiency (GHD) diagnosis in childhood is based on clinical and auxological assessment, combined with biochemical tests, but the reliability of pharmacological provocative tests in diagnosing GHD in children remains disputed. In recent years several papers have been published on standardizing the duration of the test for some stimuli. The aim of our study is to analyze the L-DOPA test, evaluating whether it is possible to shorten it to 90 minutes, without changing its validity, to reduce healthcare costs and patient’s discomfort.Methods: In a retrospective study, we investigated the response of Growth Hormone (GH) to L-DOPA test in 256 children (147 males, 109 females, 177 prepubertal, 79 puberal), analyzing a total of 267 L-DOPA test performed. The inclusion criteria were height less than -2 SD below the mean for the normal population and/or a subnormal growth velocity. Exclusion criteria were genetic, oncological, or neurological diseases. Based on the results of the stimulation tests, we divided the patients into two groups: patients with diagnosis of GHD (two different deficient provocative tests carried out in two different occasions), and patients with idiopathic short stature (ISS), who satisfied auxological criteria presenting at least one normal response to provocative tests. We analyzed the same data considering GH peak threshold value both at 8 ng/ml (value considered as the cut-off in Italy) and at 10 ng/ml (international cut-off for the diagnosis of GHD). We first described the results in the whole population and then clustering the population for gender and pubertal stage.Results: With a GH threshold value of 8 ng/ml, shortening L-DOPA test time from 120 to 90 minutes would have changed test results in 7 of the 267 analyzed tests (2.62%). With a GH threshold for the diagnosis of GHD at 10 ng/ml, shortening L-DOPA test time from 120 to 90 minutes would have changed test results in 3 of the 267 analyzed tests (1.12%).Conclusion: The L-DOPA test can be administered for 90 minutes without significantly changing its validity to minimize patient discomfort and healthcare costs.