medwireNews: Adherence to recombinant human growth hormone (GH) has a strong influence on the growth response of children with GH deficiency, especially during the second year of treatment, report researchers.

The findings emerge from an analysis of 95 prepubertal participants of the easypod Connect observational study (ECOS) who had complete data and a starting height standard deviation score (SDS) of –2.0 or below.

All these patients had idiopathic isolated GH deficiency and were taking recombinant human GH using the easypost injection device, which records the number and timing of doses, allowing an objective assessment of medication adherence.

“While automatic recording of adherence is helpful to give insight into the frequency of suboptimal adherence and its effect on the growth response to GH treatment, for clinical care its most important benefit could be that it gives the clinician a signal to intervene and try to improve adherence”, write Paula van Dommelen (TNO, Leiden, the Netherlands) and study co-authors in PLoS ONE.

The team found medication adherence to be strongly associated with the change in height SDS during 2 years of treatment, after accounting for factors including age and height SDS at GH initiation, and GH dose.

However, this effect was driven by the strong association during the second year of treatment; average adherence as a continuous variable in the first year was not significantly associated with growth response, and neither was high versus low adherence in the fully adjusted model.

The researchers say this could be partly because “the effect of GH on growth is most prominent in the first year of treatment, with a relatively strong effect on growth velocity with relatively little effect of GH dose.”

But they note it could also be due to the overall high adherence in the first year making it difficult to detect associations. In the first year, the median adherence was 95%, with a 25–75% percentile range of around 85% to 99%. In the second year, however, the median fell to about 93% and there was greater variability, with 25% and 75% percentiles of around 74% and 98%, respectively.

After 2 years of treatment, with 78% as the cutoff for high adherence, the 72% of children with high adherence had a height SDS that was 0.34 greater than that of those with low adherence, after adjustment for clinical confounders.

Missing one injection per week would result in the child missing out on 0.11 SDS worth of height gain over 2 years, say the researchers, “which implies that a daily routine of taking an injection, especially in the second year, is recommended.”

They note that while techniques such as motivational interviewing are thought to help improve treatment adherence, these have not yet been tested in controlled trials.

By Eleanor McDermid

PLoS ONE 2018; 13: e0206009

medwireNews is an independent medical news service provided by Springer Healthcare. © 2018 Springer Healthcare part of the Springer Nature group