4CPS-024 Human normal immunoglobulin requirements in paediatric patients with primary immunodeficiency, focusing on the administration route switching

Background Human normal immunoglobulin (HNIg) indications are replacement. This therapy can be administered intravenously monthly (IVIG) or subcutaneously weekly (SCIG). Due to the possibility of self-administration and a better safety profile of SCIG, this route is being increasingly preferred by patients and physicians. Purpose To describe the changes in HNIg requirements as replacement therapy in paediatric patients with primary immunodeficiency (PID), focusing on the IVIG to SCIG switching. Material and methods Based on medical history records, we collected the dosage of HNIg treatments of paediatric PID patients both on IVIG and SCIG, in our hospital over 12 months. Then we analysed the subgroup of patients treated with SCIG: we conducted a retrospective data collection of the previous IVIG requirements, the SCIG doses and the IgG plasma levels reached. Results A total of 34 patients on HNIg treatment were identified, 28 were treated with IVIG and six were treated with SCIG with a median monthly dose of 441 mg/kg and 410.8 mg/kg respectively. Focusing on the SCIG-treated patients (six active patients at the time of the study and two previously treated), with a median of 15.8 months of treatment (11–23), all of them were treated previously with IVIG, with a monthly dose of 541 mg/kg/month (442.5–702.5), reaching IgG plasma levels of 8882 mg/L (8454.5–9725). All the SCIG switches were performed using dose equivalence 1/1 of the monthly IVIG as a weekly regimen, achieving plasma levels of IgG of 10212.5 mg/L (9790.5–10847.5) on the first control (1 to 3 months after the switch). During follow-up, the monthly SCIG dose was reduced in six/eight patients (mainly by widening the administration interval from weekly to every 10 to 14 days) still keeping plasma IgG levels of 10000.5 mg/L (8515.5–10635). This dose optimisation means a 24.1% reduction between IVIG dose required previously (541.3 mg/kg/month (355–739)) to the SCIG dosing at the end of the study (410.8 mg/kg/month (332–504)). Conclusion A priori, SCIG treatments have similar dose requirements as IVIG, but we have shown that in our patients, the switch allowed a HNIg dose reduction of 24%, still keeping correct IgG plasma levels. The SCIG pharmacoeconomic profile seems to be more interesting, although other studies are lacking in validating these results. References and/or Acknowledgements Colleagues. No conflict of interest