IMPE Abstracts

Background: Pediatric growth hormone deficiency (pGHD) is treated with daily somatropin (recombinant human growth hormone) injections. High discontinuation rates and poor adherence to treatment, which may be associated with worse growth outcomes, have been documented in Japan, EU and the US.

Objectives: To describe adherence to daily somatropin treatment and assess the association between adherence and height velocity (HV) among patients with pGHD in a real-world US population within one year of treatment start.

Methods: This retrospective cohort study included patients (≥3 and <16 years old) with pGHD prescribed somatropin by a pediatric endocrinologist at the University of Minnesota Masonic Children’s Hospital between 01/01/2015 and 12/31/2020. Patient data was collected using hospital electronic health records linked to Fairview Specialty Pharmacy patient prescription records. Patients were required to have ≥1 somatropin prescription (first prescription = index date) within the study period and ≥1 height measurement during a 6-month pre-index period and ≥1 height measurement during the one-year follow-up (F/UP) period, whereby change in HV was assessed. Adherence, measured using proportion of days covered (PDC) metric, was calculated using total number of days covered over the F/UP period divided by number of days of F/UP, expressed as a percentage. Patients were categorized as adherent if PDC≥80%. Change in height was the difference between height at index and final height measured closest to one of these timepoints (whichever occurred first): one-year; end of F/UP; date of treatment discontinuation due to target height achievement; date of treatment discontinuation (measured using a >90-day treatment gap). Height change was annualized to compare across adherent and non-adherent patients.

Results: 181 patients were identified: 70.2% were male,73.5% were white. Mean age (standard deviation [SD]) at index was 12.1 (2.8). Applying PDC≥80%, 108 (59.7%) patients were adherent. 175 patients were included in the HV analysis. Mean (SD) annualized change in height was 10.2 (5.7) in the adherent group (n=108) and 9.8 (7.6) in the non-adherent group (n=67). The difference in HV between the groups was not statistically significant.

Conclusions: Minor improvements in average HV were observed in the patient group who were adherent to somatropin therapy, although not statistically significant. Lack of observed significance may be due to small sample sizes, data bias due to single-center origin or potential patient misclassification. Further studies in different databases or an encore study using this database when more patients are available may be warranted.