The diverse nature of the heterogeneous etiological and clinical spectrum of the MetabERN disease panel necessitates the limitation of data collection to a minimal set of common data elements and the usage of controlled and standardized vocabularies for the description of the clinical phenotype and treatment strategies. The U-IMD registry will collect data using four modules:

Module 1: Common Data Elements

The registry contains a module of common data elements that is uniform across all diseases. U-IMD uses the set of common data elements developed specifically for rare disease registration by the European Commission's Joint Research Centre (DG JRC). The usage of these common data elements is recommended as a constitutive element for all rare disease registries in Europe. It is a necessary prerequisite for working with the European Rare Disease Registry Infrastructure (ERDRI), a set of tools developed by the DG JRC EU as part of the Rare Diseases Registries Platform (EU RD Platform) that aims to cope with the enormous fragmentation of data collected by rare disease registries
throughout Europe. Cases are defined using the Inborn Errors of Metabolism Knowledgebase, which is also mapped to Orpha Codes and OMIM Codes.

Module 2: Clinical and biochemical phenotype

The registry contains a module for clinical phenotyping that is uniform across all diseases. This module uses the Human Phenotype Ontology as an established, controlled and standardized vocabulary for phenotyping clinical abnormalities, thus ensuring interoperability with other registries
using the same vocabulary for phenotyping and comparability of phenotypes across all diseases in the registry. In addition to HPO, results of standard IQ tests are included.

Module 3: Patient perspective

The registry contains a module for adequately capturing the patient perspective that is uniform across all diseases. PedsQL and WHOQOL-BREF questionnaires can be filled in by the patients directly
and have been translated and validated in multiple languages. These tools have already been successfully used in the E-IMD, E-HOD and iNTD registries.

Module 4: Treatment

The registry contains a module for capturing drug treatment that is uniform across all diseases. This module uses the WHO ATC classification system as an established, controlled and standardized
vocabulary. WHO ATC codes drugs with a five-tiered classification system, from the treated organ system down to the respective chemical substance. Off-Label or Orphan drug usage will be recorded.

Module 5: Biochemical markers

The registry contains a module for recording the results from laboratory tests. The registry uses disease specific sets of biochemical markers established by the Inborn Errors of Metabolism Knowledgebase which are also mapped to the Human Metabolome Database (HMDB).

Module 6: In addition to collaborations among experts within a field in the framework of European Reference Networks, collaboration between different European Reference Networks is of great importance. Therefore U-IMD as registry of the MetabERN collaborates with ERKReg, the registry of the European Rare Kidney Disease Reference Network. U-IMD includes all disease progression parameters of ERKReg for diagnoses classified as metabolic nephropathies.