Methodology for the international working group clinical practice guidelines on X-linked hypophosphatemia in children and adults

The guideline panel, comprising international experts in X-linked hypophosphatemia (XLH), patient partners from the XLH patient population, and guideline methodologists, held 18 teleconferences between January 2023 and July 2024 to develop comprehensive guidelines for the diagnosis and management of XLH in children and adults. For a subset of our questions, we utilized the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology, assessed the certainty of evidence and formulated GRADEd recommendations. For these questions, the panelists and methodologists collaboratively framed PICO (Population, Intervention, Control, and Outcomes) questions and conducted four systematic reviews assessing the impact of medical therapy-using either burosumab or phosphate and active vitamin D-on patient-important outcomes in the XLH population as well as the impact of medical intervention compared to no treatment. We assessed the risk of bias and transparently generated summary of findings tables using MAGICApp. The panel developed three GRADEd treatment recommendations for adults and two for children. Each GRADEd recommendation was linked to an underlying body of evidence, reflecting judgments on the certainty of evidence, recommendation strength, values, preferences, and considerations of costs, feasibility, acceptability, and equity. Due to the paucity of evidence, the panel developed very low-quality GRADEd recommendations on monitoring patients with XLH based on an expert clinical practice survey. Using a rigorous narrative literature review, the panel developed non-GRADEd recommendations including guidance for pregnant women, patients with dental complications, and other areas where evidence is limited. This article summarizes the methodology utilized for the development of both GRADEd and non-GRADEd recommendations for patients with XLH.