Standardizing Rare Disease Data in Brazil: A Delphi-Based Approach for the First National Registry

Introduction: Rare diseases (RD) are characterized by low prevalence, affecting fewer than 1 in 2,000 individuals, yet impacting millions globally. In Brazil, RD management is challenged by geographic disparities and unequal access to care. To address these gaps, the Brazilian Rare Diseases Network (RARAS) developed a Minimum Data Set (MDS) to standardize RD documentation. Objective: To validate the proposed MDS through a Delphi consensus process with clinical experts. Methods: This study used the Delphi method to validate the MDS, involving clinical experts. A structured questionnaire with 55 items across nine data categories was distributed via REDCap. Experts evaluated the relevance of each variable and reached a consensus, which was defined as ≥80% agreement. Results: Fifty-two professionals were invited; 16 responded in round one, and 11 in round two. Suggestions for additions and removals were reviewed after each round. Seven data categories achieved over 81.8% agreement, reaching consensus levels between 90.9% and 100%. The final MDS includes care indicators and facilitates consistent documentation and care coordination. Conclusions: This study demonstrates the value of standardized data collection in strengthening RD surveillance, clinical workflows, and research.