OBJECTIVES:

X-linked hypophosphataemia (XLH) is a rare, progressive, hereditary phosphate-wasting disorder characterised by excessive fibroblast growth factor 23 (FGF23) activity. The International XLH Registry was established to provide information on the natural history of XLH and impact of treatment on patient outcomes. Most XLH research has investigated genetics, biochemistry, and skeletal deficits. However, more understanding of the XLH impact on patients’ lives is needed. Real-world (RW) evidence, in which patient-reported outcomes (PROs) play a central role, provides unique information on the impact of medical conditions and treatments from patients’ perspective, without external interpretation. PROs are increasingly recognised as valuable tools to collect patient-centred data and are seen as robust endpoints. PROs are included in many clinical trials and a post-hoc clinical trial analysis showed treatment with burosumab, a human monoclonal FGF23 antibody, improved PROs in adults with XLH (24 and 96 weeks). Inclusion of PROs in the Registry provides opportunity to evaluate XLH burden in a RW population over a longer period.

METHODS:

The International XLH Registry (NCT03193476), initiated August 2017, aims to recruit 1,200 children and adults with XLH, running for 10 years. The Registry captures PROs to describe the impact of XLH and treatment on patients’ quality of life, daily activities, and symptoms.

RESULTS:

The number of completed PRO assessments to date (SF-36 and PedsQL surveys) total >140, continuing to rise. As of 31/5/2022, there were 805 eligible subjects (UK, 321; France, 272; Italy, 110; Spain, 59; Sweden, 43) – 43% adults, 57% paediatric subjects, 63% female.

CONCLUSIONS:

This is the largest RW dataset of subjects with XLH collected to date. Interim analyses of this RW PRO dataset, stratified to country, age, sex, treatment effectiveness, is scheduled for 2023. PROs gathered during the 10-year duration of the Registry will generate robust RW evidence and help inform healthcare decision making.