OD4RD - Codification of Rare Diseases

Last updated on 9-2-2024 by Annabelle Calomme
Project duration:
January 1, 2022
December 31, 2025

In short

The field of rare diseases (RD) is one where the value of transnational data collection, sharing and exploitation for evidence-based policy, healthcare and research has been clearly demonstrated and targeted by several European initiatives. Rare diseases are collectively widespread (the number of European citizens affected is estimated at more than 30 million) but individually rare (there are more than 6,000 clinically defined rare diseases to date). Therefore the critical amount of data necessary to improve knowledge and policies can only be achieved through cumulative data collection across countries in a standardised way.

Rare diseases are still poorly represented in the medical terminologies commonly used. There is no terminology dedicated to these conditions, with the exception of the multilingual standardized specific terminology developed by Orphanet, the international reference portal for rare diseases and orphan drugs. Orphanet developed and continuously updates the Orphanet nomenclature and classification of rare diseases, essential in improving the visibility of RDs in health and research information systems. Each clinical entity referenced in Orphanet is assigned a unique, time-stable and non-reusable numerical identifier, the ORPHAcode, around which the rest of the data present in the Orphanet database is structured. 

One of the main objectives of the Orphanet Data for Rare Disease project (OD4RD), co-funded by the EU4Health programme of the European Commission, is to advance the implementation of ORPHAcodes in hospitals hosting member centres of European Reference Networks (ERNs) and to use the expertise of ERNs to further improve the Orphanet nomenclature. This should make it possible to establish a common language, with codes specifically created for rare diseases, to effectively monitor and report on rare diseases (including undiagnosed cases). 

The OD4RD project contributes to improving the diagnosis and management of patients, as the widespread use of ORPHAcodes will improve the accuracy of coding patients with rare diseases in health-related information systems and facilitate collection, research and analysis of data at European level.

Project description

The OD4RD project has been launched in January 2022 for a period of 15 months (OD4RD1). During this pilot phase, a network of national hubs in 13 Member State countries (Austria, Belgium, Czech Republic, Finland, Germany, Italy, the Netherlands, Norway, Poland, Portugal, Spain, Sweden, Slovenia) has been developed (in addition to Switzerland being an observer). In Belgium, the OD4RD project is managed by the Sciensano Rare Diseases Team which participates in work package 4: “Develop national Orphanet nomenclature hubs”

The European OD4RD project builds on Orphanet’s specific expertise and its long-lasting, well-established network, to fulfil the following general objectives

  1. To contribute to the generation of standardised, interoperable data on RD diagnosis, through maintenance of the Orphanet nomenclature of RDs in collaboration with ERNs, and active support for its implementation in hospitals hosting ERNs;
  2. To contribute to the harmonisation of data collection in various settings (health records, registries) and countries, through dissemination of good coding practices; 
  3. To support evidence-based decision making in the context of the European strategy on ERNs, by providing a usable reference corpus of data on RDs. 


At Sciensano, we undertake different actions to achieve the deliverables stated in OD4RD-WP4:

  • Development of a national action plan: at the beginning of the OD4RD project, a state of play survey was launched to assess each national situation regarding the implementation of ORPHAcodes. A report compiled from the survey showed that the overall picture of RD coding with ORPHAcodes is very different between the participating countries. It ranges from already implemented ORPHAcodes in national coding systems used in all hospitals, to not yet using ORPHAcodes at all. In Belgium, the situation is complex because of the planned transition to SNOMED CT® as the common national reference terminology in all electronic health records. Based on the results of the state of play survey, we created a Belgian Action Plan.
  • Organisation of training sessions in national languages: we provide training sessions on Orphanet nomenclature and classification in several languages (French, Dutch and/or English) to clinicians, coders, hospital information managers, statistical services and other stakeholders involved in rare diseases. There are various possibilities in terms of methods (online, on site), duration (from 2 hours to a day, depending on availability and needs) and testing of knowledge autonomously via online quizzes. Anyone who is interested in receiving a training can contact our team at Orphacodes.Belgium@sciensano.be.
  • Promotion of the Orphanet nomenclature: each OD4RD national hub participates in advocating ORPHAcodes towards national decision makers (e.g. Ministry of Health, federal and regional institutions, hospital managers) using promotional material (guidelines, flyers, videos, etc.).
  • Support in the use of the Orphanet nomenclature through​ a national helpdesk: the helpdesk is dedicated to answering questions related to the Orphanet nomenclature content and the implementation of ORPHAcodes in local health information systems. A central OD4RD Github allows requests to be tracked and monitored. A FAQ section has been developed and is continually updated based on users’ questions, transmitted by each participating country, including Belgium. 

The pilot phase ended in March 2023 and a report on lessons learned was produced based on the feedback sent by each participating country, including Belgium, to provide guidance to other countries starting to implement ORPHAcodes. 

The project has been renewed until the end of 2025 (OD4RD2). During this second phase (April 2023-December 2025), 6 new countries (Bulgaria, Estonia, Ireland, Latvia, Lithuania and Romania) joined the project, with the aim of establishing a network of 19 autonomous national hubs (+1 observer). The OD4RD2 project aims to increase the number of collaborations with ERNs and to develop adapted material allowing health professionals to better deal with the difficulties that may be encountered when coding rare diseases.

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