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In healthcare, diagnostic codes are used to group and identify diseases, disorders, symptoms, human response patterns, and medical signs, and are used to measure morbidity and mortality. As the plural with the name of this lemma indicates, there will be never one code for all purposes, but many codes for some distinct purposes each.

The codes may be quite frequently revised as new knowledge is attained. DSM (see below) changes some of its coding to correspond to the codes in ICD. In 2005, for example, DSM changed the diagnostic codes for circadian rhythm sleep disorders from the 307-group to the 327-group; the new codes reflect the moving of these disorders from the Mental Disorders section to the Neurological section in the ICD.[1]

Commonly used diagnosis coding systems

Systematized Nomenclature of Medicine


Generally coding is a concept of modeling reality with reduced effort but with physical copying.

  • Hence the result of coding is a reduction to the scope of representation as far as possible to be depicted with the chosen modeling technology. There will be never an escape, but choosing more than one model to serve more than one purpose. That led to various code derivatives, all of them using one basic reference code for ordering as e.g. with ICD-10 coding. However, concurrent depiction of several models in one image remains principally impossible.
  • Focusing a code on one purpose lets other purposes unsatisfied. This has to be taken into account when advertising for any coding concept. The operability of coding is generally bound to purpose. Inter-referring must be subject of evolutionary development, as code structures are subject of frequent change.[2]
  • Unambiguous coding requires strict restriction to hierarchical tree structures possibly enhanced with multiple links, but no parallel branching for contemporary coding whilst maintaining bijectivity.
  • Spatial depictions of n-dimensional code spaces as coding scheme trees on flat screens may enhance imagination, but still leave the dimensionality of image limited to intelligibility of sketching, mostly as a 3D object on a 2D screen. Pivoting such image does not solve the intelligibility problem.
  • Projections of code spaces as flattened graphs may ease the depiction of a code, but generally reduce the contained information with the flattening. There is no explanation given with many of the codes for transforming from one code system to another. That leads to specialized usage and to limitations in communication between codes. The escape is with code reference structures (as e.g. not existing with SNOMED3).
  • Hierarchical ordering of more than one code system may be seen as appropriate, as the human body is principally invariant to coding. But the dependency implied with such hierarchies decrease the cross referencing between the code levels down to unintelligibility. The escape is with hyper maps that exceed planar views (as e.g. with SNOMED3) and their referring to other codes (as e.g. yet not existing with SNOMED3).
  • Purpose of documenting will be seen as essential just for the validation of a code system in aspects of correctness. However this purpose is timely subordinate to the generating of the respective information. Hence some code system shall support the process of medical diagnosis and of medical treatment of any kind. Escape is with a specialised coding for the processes of working on diagnosis as on working with treatment (as e.g. not intended with SNOMED3).
  • Intelligibility of results of coding is achieved by semantic design principles and with ontologies to support navigating in the codes. One major aspect despite the fuzziness of language is the bijectivity of coding. Escape is with explaining the code structure to avoid misinterpreting and various codes for the very same condition (as e.g. yet not served at all with SNOMED3).


  1. First, Michael B. (2005). New Diagnostic Codes for Sleep Disorders. American Psychiatric Association. URL accessed on 2008-08-08.
  2. Towards Semantic Interoperability in Healthcare

See also

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