Alpha-ID - an identification number for diagnoses

Alpha-ID permits the encoding of medical and natural language diagnostic terms. Published in 2005 by DIMDI as a prototype, Alpha-ID is based on the Alphabetical Index of ICD-10-GM. Each alphabetical entry is allocated a sequential and stable identification number: the Alpha-ID code. It provides a unique identification for each entry and thus assumes the function of a non-classifying diagnostic code.

Alpha-ID-SE - Scope of application "Rare Diseases"

Alpha-ID is available as electronic version (TXT (CSV)) and is updated annually. The currently valid version is effective from the beginning until the end of a calendar year.

Differentiated diagnostic codes for medical documentation

Classification always entails a loss of detailed information: for example, the ICD-10 classification combines all synonymous terms for a particular disease as well as similar diseases within the same class under a single code. ICD codes are thus not sufficiently differentiated to be used in documentation for therapeutic purposes. By contrast, Alpha-ID allows all synonymous terms and each individual name for a disorder from the alphabetical index as a separate identifier. Each entry has its own Alpha-ID code - an individual, utterly unique, non-classifying identification number.

Example: There are 28 entries in the Alphabetical Index for the ICD-10-GM code "L30.8 Sonstige näher bezeichnete Dermatitis"(Other specified dermatitis), all encoded as L30.8. In Alpha-ID, each of these entries is given its own Alpha-ID code as in the following four entries:

Alpha-ID-Code ICD-10-GM-Code Entry
I6158 L30.8 Ichthyosiformes Ekzem
I6159 L30.8 Nässendes Ekzem
I6154 L30.8 Nässender Nabel
I6142 L30.8 Trockenes Ekzem


The Alpha-ID represents the complete information of the respective entry, but is easier to exchange in electronic communication than non-standardised uncoded text. In that way, it provides diagnostic codes for more than 80,000 differentiated diagnostic terms, each of which is also assigned the appropriate ICD-10-GM code.

Alpha-ID versus Alphabetical Index

In contrast to the Alphabetical Index of ICD-10-GM, the Alpha-ID is cumulative: Entries deleted as part of ICD-10-GM database maintenance are retained in Alpha-ID with the appropriate designation. The current version of Alpha-ID can thus also be used to decode identification numbers that refer to previous entries.

In contrast with the ICD-10-GM codes, Alpha-ID identification numbers are stable. In Alpha-ID, each entry has two codes: the unique identification number and the associated ICD code. New insights in medicine or restructuring of the ICD-10-GM database can result in changes to the ICD code for a particular entry. By contrast, an Alpha-ID, once assigned, remains linked to its entry unchanged forever.

Alphabetical Index of ICD-10-GM


Interoperability is defined as the ability of different systems to successfully communicate with each other. This requires standardisation. The increasing level of electronic communication in the health care sector (keyword: eHealth) requires diagnostic codes for therapeutic use that are understood by all participating systems. Alpha-ID permits nationwide standardised diagnostic encoding for electronic communication across all of Germany.

Alpha-ID proposal procedure

The Alpha-ID is subject to ongoing development. At present, it is annually adapted to changes in the Alphabetical Index resulting from the proposal procedure for ICD-10-GM. In addition, you have the opportunity continuously to improve Alpha-ID with suggestions of your own. Please submit suggestions for Alpha-ID during the proposal procedure for ICD-10-GM (always from December to the end of February) in an informal e-mail to classifications.

Contact Form

Proposal Procedure of ICD-10-GM

Alpha-ID-SE - Scope of application "Rare Diseases"

(c) Leigh Prather / Fotolia

DIMDI publishes, in the context of the project "Rare diseases coding", a test file of the Alpha-ID (starting with version 2015) which contains the Orpha number in addition to the ICD-10-GM code for rare diseases.

The Alpha-ID-SE (rare diseases) allows a simplified, uniform and standardised coding of rare diseases according to ICD-10-GM on one hand, and to the Orpha number on the other hand. This improves documentation and leads to an adequate representation of rare diseases in the German healthcare sector. Furthermore, the Orpha numbers allow connections to reference systems for rare diseases throughout Europe.

DIMDI also worked on the improvement of the codification of rare diseases (RD) in the framework of the European project "Rare Disease Action" (RD-Action, finished July 2018). The primary aim of this project was to improve the visibility of rare diseases at European level.

Rare Diseases, ICD-10 and Orphanet

What are rare diseases?

There is no widely accepted definition for rare diseases. In Europe a prevalence of not more than 5 affected persons per 10.000 is generally regarded as the appropriate threshold, according to the Regulation of the European Parliament and of the Council on orphan medicinal products.

Regulation (EC) No 141/2000 of the European Parliament and of the Council of 16 December 1999 on orphan medicinal products

Coding rare diseases with ICD-10-GM: unspecific in most cases

More than 4 million people in Germany suffer from a rare disease. It is estimated that about 8000 distinct rare diseases affect the population worldwide. Rare diseases are so numerous that as a whole they are as frequent as a widespread disease. Nonetheless, rare diseases are barely perceptible from an epidemiological perspective.

Only few rare diseases can be specifically coded with ICD-10, in other words, they have an own code. Most of them are classified as "inclusions" of an unspecific ICD-10 code. Therefore a large number of rare diseases can no longer be identified by means of the ICD-10 code. Moreover, many rare diseases are still not listed in the Alphabetical Index of ICD-10.

In order to make rare diseases visible in epidemiology, they must be coded as specifically and precisely as possible.

Orphanet rare disease nomenclature as a specific coding system for rare diseases

Orphanet, a European reference portal for information on rare diseases and orphan drugs, offers a specific coding system with its nomenclature. All rare diseases in this nomenclature have been assigned a consecutiv, specific identification number, the Orpha number (so-called "Orphacode").

Via its website Orphadata, Orphanet provides information regarding its nomenclature system and the connection to other code systems and terminologies such as ICD-10, MeSH, OMIM, MedDRA, and UMLS - free of charge.

The European Council has recommended in 2014 that all Member States of the European Union "[…] should consider adding Orpha codes to their country’s health information system […]".

National DIMDI Project "Kodierung von Seltenen Erkrankungen" (Rare diseases coding)

In order to code rare diseases specifically in Germany, Orpha numbers should be used in addition to the ICD-10-GM code which is compulsory in inpatient and outpatient routine coding. Therefore coders would need to use two coding systems.

The goal of the DIMDI project "Rare diseases coding" is to improve the coding of rare diseases and to simplify this "double" coding process. The project is an initiative in the context of the National Action Plan for People with Rare Diseases. It was initiated in July 2013, was set up for three years and has been extended until the end of June 2019.This project is financed by the Federal Ministry of Health (BMG).

Addition of rare diseases to the Alphabetical Index of ICD-10-GM and Alpha-ID

This project initially reviews whether all rare diseases listed in the Orphanet nomenclature are included in the Alphabetical Index of ICD-10-GM. Diseases that are not included will be added and assigned to an ICD-10-GM category. In addition, there will be a reconciliation with Orphanet for all ICD-10 codes that are already mapped to the rare diseases of the Orphanet nomenclature.

This first step will lead to a better representation of rare diseases in ICD-10-GM and thus to improved coding.

When a rare disease is added to the software version of the Alphabetical Index of ICD-10-GM, a specific identification number is assigned to every term. With this specific identification number and the ICD-10-GM code rare diseases are then also included in the Alpha-ID file, which DIMDI publishes on an annual basis.

Test file Alpha-ID-SE with Orpha numbers

To further improve the documentation of rare diseases, Orpha numbers are added to the rare disease entries of the Alpha-ID and published in a project-specific test file, the Alpha-ID-SE. This connection of ICD-10-GM codes and Orpha numbers in the Alpha-ID-SE makes it possible to code rare diseases in Germany in a more differentiated and specific manner by means of a file.

The "Musterdatensatz", an extract of the test file Alpha-ID-SE is a sample data set that only includes rare diseases with the assigned Orpha number. A test implementation of this "Musterdatensatz" is performed in 4 selected reference centers for rare diseases as part of the project. As a result of the project DIMDI will issue a recommendation to a nationwide routine implementation.

The following exemplary extract from the test file Alpha-ID-SE shows that synonymous terms of rare diseases such as, for instance, Fibrodysplasia ossificans progressiva and Münchmeyer-Syndrom have the same Orpha number (337) and the same ICD-10-GM code (M61.19), but different Alpha-ID codes: This is the concept of Alpha-ID, every text entry has its own Alpha-ID code.

Please note that the Alpha-ID is based on the Alphabetical Index of the ICD-10-GM, and that Alpha-ID codes are only assigned to diagnostic terms in German language. Therefore the use of Alpha-ID codes for files in other languages does not apply.

The test file also shows that several distinct rare diseases such as, for instance, the Zerebro-hepato-renales Syndrom (Cerebrohepatorenal syndrome) and Lymphödem mit Hypoparathyreoidismus (Lymphedema-hypoparathyroidism syndrome) may be assigned the same ICD-10-GM code (Q87.8), but aside from different Alpha-ID codes may also have different Orpha numbers (912 and 1563 respectively). This example shows that distinguishable diseases can not be identified by using only the ICD-10-GM code.

The example of the test file below also clarifies the relation between the ICD-10-GM code and the Orpha number, for instance: diseases like Apfelschalensyndrom (Apple peel syndrome), Jejunalatresie (Jejunal atresia) and Dünndarmatresie (Atresia of small intestine), may all have the same Orpha number (1201) but in some cases a different ICD-10-GM code (in this case Q41.1 or Q41.9). It illustrates the diverse criteria two different systems, like the Orphanet rare disease nomeclature and the ICD-10-GM use to classify diseases. In this case the ICD-10-GM uses the localization as further classification criteria (Q41.1 concerns the atresia of jejunum and Q41.9 the atresia of the small intestine, part unspecified).

In case of the synonyms Intestinale Lipodystrophie (Intestinal lipodystrophy) and Whipple-Krankheit (Whipple disease), which have the same Orpha code (3452), one synonym is coded with a single ICD-10-GM code (K90.8), the other one with an additional asterisk code (K90.8+ M14.89*) to indicate the manifestation.

Excerpt from the test file Alpha-ID-SE/ "Musterdatensatz"

Alpha-ID-Code ICD-10-GM-Code ICD-10-GM-Additional (Asterisk) Code Orpha Number Diagnostic Term
I5821 K90.8 unfilled 3452 Intestinale Lipodystrophie
I24937 K90.8+ M14.89* 3452 Whipple-Krankheit
I32050 M61.19 unfilled 337 Fibrodysplasia ossificans progressiva
I81949 M61.19 unfilled 337 Münchmeyer-Syndrom


Q41.1 unfilled 1201 Apfelschalen-Syndrom
I118177 Q41.1 unfilled 1201 Jejunalatresie
I17291 Q41.9 unfilled 1201 Dünndarmatresie


Q87.8   912 Zerebro-hepato-renales Syndrom
I118259 Q87.8 1563 Lymphödem mit Hypoparathyreoidismus

The test file Alpha-ID-SE is a basis for the completion of other actions of the National Plan of Action for People with Rare Diseases, for example the creation of a registry prototype or the "se-atlas" [a web portal that maps care providers for persons with rare diseases].

Furthermore, the file is available to any user who strives to create a differentiated depiction of rare diseases. For example, the access to information from Orphanet regarding certain rare diseases can be simplified via the connection of ICD-10-GM codes and Orpha numbers by providing corresponding references to Orphanet for the user during the coding process with ICD-10-GM.

The project-specific test file Alpha-ID-SE is included as electronic version (TXT (CSV) in the ZIP file for Alpha-ID. It is updated annually. The currently valid version is effective from the beginning until the end of a calendar year. The "Musterdatensatz" 2019 includes all 5.208 entries of Alpha-ID-SE for rare diseases thus far. In the case of corrections during this period of validity you will be informed by our Newsletter DIMDI News.

International EU Project "RD-Action" (Rare Disease Action)

(c) fotomek / Fotolia

DIMDI works on the improvement of the codification of rare diseases (RD) on an international level for example in the framework of the European project "Rare Disease Action" (RD-Action), which ended in July 2018.

The cooperation of different countries in the thematic field of RD proved to be useful in the past. RD-Action large geographical coverage is key to success since it promotes the transfer of European recommendations into national policies and the collection of information and concerns from Member States (MS) to the Commission Expert Group on Rare Diseases (CEGRD), thus to the European Commission.

With 34 beneficiaries and 30 collaborating partners from 40 participating countries, the RD-Action aimed at creating a consistent European way of meeting challenges in the field of RD. Besides EU-countries, other European countries like Iceland and Switzerland as well as non-European countries like Canada and Australia participated in the RD-Action and thus involved in international developments in the field of RD. One objective of the RD-Action was to support the development and sustainability of the Orphanet database. A second objective has been the contribution to solutions to ensure an appropriate codification of RD in health information systems across Europe. Besides that, the work on priority issues for people living with RD by implementing the actions defined in the EU Council Recommendation on an action in the field of RD and to ensure the sustainability of these actions as well as supporting the work of the CEGRD were further objectives.

The 3-year European Joint Action started in June 2015 and ended in July 2018. It has been co-financed by the European Commission.

Content of the project

RD-Action consisted of 6 Workpackages (WP). DIMDI lead the WP 5, Steering, maintaining and promoting the adoption of Orphacodes across MS.

Workpackage 5: Steering, maintaining and promoting the adoption of Orphacodes

With the recommendation of the European Council of 2009 on an action in the field of RD all MS should amongst others "aim to ensure that rare diseases are adequately coded and traceable in all health information systems […]":

COUNCIL RECOMMENDATION of 8 June 2009 on an action in the field of rare diseases (2009/C 151/02)

The RD-Action aims to put into effect this part of the council recommendation at European level.

The WP 5 has been divided into 4 different tasks. The tasks were building on each other in time and content. The following tasks were performed:

  • Task 5.1. To define and set the necessary strategy and tools (i.e. coding rules) to implement the Orphacodes in the European countries.
  • Task 5.2. Specifications of the required resources (i.e. Master file) for coding RD consistently across Europe.
  • Task 5.3. Promoting the Orphacodes across MS by sharing coding tools and testing the master resource.
  • Task 5.4. Plan for next steps needed to address long-term maintenance and sustainability of the resources and guidelines.

DIMDI has been responsible for the achievement of task 5.2. Within this task a Master file (Master file for statistical reporting with Orphacodes) has been developed. Comparable to the "Musterdatensatz", which is produced in the framework of the national project, the master file should enable an easy and standardized way to code RD across MS.

The Master file as well as the developed recommendations for coding of rare diseases are available for download on the RD Action website, Chapter "Leaflet & Documents" (see link at "Additional information about the international EU project on the web").

Additional information about the international EU project on the web


This website is part of the project / joint action '677024 / RD-ACTION' which has received funding from the European Union’s Health Programme (2014-2020).

The content of this website represents the views of the author only and is his/her sole responsibility; it cannot be considered to reflect the views of the European Commission and/or the Consumers, Health, Agriculture and Food Executive Agency or any other body of the European Union. The European Commission and the Agency do not accept any responsibility for use that may be made of the information it contains.