Creation and Validation of the Major Pediatric Mitochondrial Cytopathies Minimum Data Set: Consensus from a...

Background: Pediatric mitochondrial cytopathies (MCs) are rare, multisystemic, and heterogeneous disorders that require harmonized collection of clinical, biochemical, and genetic data to better understand their natural history, optimize patient care, and support translational research. In this context, developing a regionally adapted Minimum Data Set (MDS) is a critical step toward establishing a structured registry. Methods: A two-round Delphi study was conducted involving 16 Moroccan-Tunisian experts from diverse specialties to assess the relevance of 382 initially proposed variables. Robust statistical analyses were applied to all composite questions using Content Validity Index (CVI), Kappa coefficient, and Content Validity Ratio (CVR), alongside retention rate assessments. Results: The overall relevance score assigned by the experts was high (4.5 ± 0.41), with a final retention rate of 90.1% (347 variables retained out of 382). Section-wise S-CVI/Ave scores ranged from 0.91 to 0.99, with the paraclinical section achieving the highest value (0.99) and the evolutive section the lowest (0.91). The more stringent S-CVI/UA revealed greater variability (from 0.36 in clinical data to 0.83 in paraclinical data). Kappa index calculations led to the exclusion of a subclass of five therapeutic variables due to insufficient inter-rater agreement. The CVR further supported the content validity of the 46 retained subclasses. The results demonstrated strong consensus, particularly across the neurological, biochemical, molecular, and medical follow-up domains. Additionally, the registry design survey revealed strong expert support for a secure and interoperable digital platform incorporating longitudinal follow-up and advanced search and reporting functionalities. Conclusions: This validated Moroccan-Tunisian pediatric MDS offers a solid foundation for a regional mitochondrial cytopathy registry. It standardizes data collection, strengthens clinical research, and improves diagnosis and care for affected children in the Maghreb. Moreover, it lays the groundwork for future interoperability with international registries, contributing to a more inclusive and collaborative precision medicine landscape.