medwireNews: Researchers say that the optimal cutoffs for detecting children with growth hormone deficiency (GHD) are considerably lower than current recommendations.

“Although current guidelines still indicate a cut-off of 10 μg/L, such value is not supported by robust clinical data and, most likely, produces a high number of false positive results”, say Sandro Loche (Ospedale Pediatrico Microcitemico “A. Cao”, Cagliari, Italy) and colleagues.

Their study, published in the European Journal of Endocrinology, found much lower optimal peak GH cutoffs, of 5 to 6 µg/L.

The findings are based on data from 372 children who underwent GH stimulation tests with at least one of arginine, clonidine or the insulin tolerance test (ITT) at five Italian paediatric centres. Of these children, 74 proved to have GHD of organic origin, mostly caused by central nervous system tumours.

Of note, between 10 and 50 children had an abnormal response to one of these tests at the first attempt (ie, peak GH <10 μg/L), but a normal response to a second test.

The researchers conducted area under the receiver operating characteristic curve analysis and found that GH stimulation with arginine was 93.4% sensitive and 92.1% specific for GHD. However, this was not at a peak GH cutoff of 10 µg/L, but of 6.5 µg/L.

Likewise, stimulation with clonidine was 88.5% sensitive and 97.4% specific at a cutoff of 6.8 µg/L, and ITT was 91.3% sensitive and 91.7% specific at the even lower cutoff of 5.1 µg/L.

“Thus, based on these results, new normal values for the GH peak after stimulation test should be established”, say Loche and team.

Insulin-like growth factor I (IGF-I) standard deviation score was not particularly accurate for identifying GHD, with a sensitivity of 79.3% and specificity of 75.0%. When combined with GH stimulation tests, it reduced the sensitivity of all tests, but improved the specificity.

“Thus, combining the results of the stimulation tests with IGF-I measurement reduces the risk of false negative results”, say the researchers.

By Eleanor McDermid, Senior medwireNews Reporter

Eur J Endocrinol 2016; Advance online publication

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