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• Using Codes
• Code Systems
• Value Sets
• Concept Maps
• Identifier Systems

4.2.11 Using ICD-[X] Codes with FHIR

Vocabulary Work Group

Maturity Level: 2

Ballot Status: Trial Use

ICD is a family of code systems maintained by WHO , with many countries publishing their own variants.

The are two principal revisions of ICD in use - ICD-10 and ICD-9 (note that while US usage has recently updated to ICD-10, there is still a lot of legacy data coded in ICD-9). Though these can be referred to as different versions of ICD, they are entirely distinct sets of codes, with significant differences in organization and coding rules. Plus, if period ('.') characters are disregarded (as occurs in some systems), a few of the codes are overlapping between ICD-9 and ICD-10. Given these considerations, ICD-9 and ICD-10 are represented as entirely separate code systems. The next revision, ICD-11, is scheduled for release in 2017.

4.2.11.1 Summary

	ICD-10	ICD-9
Source	WHO or see below	(CDC )
System	http://hl7.org/fhir/sid/icd-10 and http://hl7.org/fhir/sid/icd-10-[x] (see below)	http://hl7.org/fhir/sid/icd-9-cm
OID	2.16.840.1.113883.6.3	2.16.840.1.113883.6.42
Version	The versioning convention and frequency may vary between the various ICD revisions and variants. WHO publishes a new version of ICD-10 annually in October (with minor updates annually, and major updates, if required, every 3 years - the versions are identified as 'YYYY', e.g. '2016'). The national variants (which in some cases are used multi-nationally) are also typically published on an annual basis (refer to the documentation for a particular variant for details).
Code	Either an ICD-10 or ICD-9 code, or a dual coding expression - see below
Display	There are no specific conventions required or described for obtaining the complete display string for use for each code.
Inactive	ICD-9 and ICD-10 do not have codes that are identified as inactive (although in some cases previously included codes may have been removed or changed in meaning in subsequent versions).
Hierarchy	The tabular representations are organized with headings and multiple levels of codes (typically based on the numbers of digits contained in each code), but an explicit hierarchy is not defined.
Filter Properties	None are described yet.

4.2.11.2 ICD-10 variants

Variants (other variants exist which are not listed here):

4.2.11.3 Dual Coding

Note that for dual coding (see volume 2 ICD-10 Manual ), section 3.1.3 Two codes for certain conditions), simply use the two ICD-10 codes separated by a space, e.g. "J21.8 B95.6".

Dual coding in ICD-10 is used for the following (and potentially other) reasons:

• Coding for diagnostic statements containing information about both (1) an underlying generalized disease and (2) a manifestation in a particular organ or site which is a clinical problem in its own right. This is referred to as the "dagger and asterisk" system, as it marks the primary code for the underlying disease with a dagger (†) and an optional additional code for the manifestation with an asterisk (*).
• Other optional dual coding (noted in the tabular representation as “Use additional code, if desired ...”)
• For local infections, classifiable to the “body systems” chapters, codes from Chapter I may be added to identify the infecting organism, where this information does not appear in the title of the rubric.
• For neoplasms with functional activity. To the code from Chapter II may be added the appropriate code from Chapter IV to indicate the type of functional activity.
• For neoplasms, the morphology code from Volume 1, although not part of the main ICD, may be added to the Chapter II code to identify the morphological type of the tumour.
• For conditions classifiable to F00-F09 (Organic, including symptomatic, mental disorders) in Chapter V, where a code from another chapter may be added to indicate the cause, i.e. the underlying disease, injury or other insult to the brain.
• Where a condition is caused by a toxic agent, a code from Chapter XX may be added to identify that agent.
• Where two codes can be used to describe an injury, poisoning or other adverse effect: a code from Chapter XIX, which describes the nature of the injury, and a code from Chapter XX, which describes the cause.

For "dagger and asterisk" coding of an underlying generalized disease and a specific manifestation, it is recommended that the primary code for the underlying disease is listed first.

Dual Coding Example: "Staph aureus bronchiolitis" is coded using ICD-10 codes J21.8 "Acute bronchiolitis due to other specified organisms" and B95.6 "Staphylococcus aureus as the cause of diseases classified to other chapters" as

  <coding>
    <system value="http://hl7.org/fhir/sid/icd-10"/>
    <code value="J21.8 B95.6"/>
  </coding>

4.2.11.4 Copyright/License Issues

ICD-10 is ©Copyright World Health Organization (WHO). WHO licenses its published material widely, in order to encourage maximum use and dissemination. See Licensing WHO classifications for details. The ICD variants have their own separate copyright and licensing (refer to the documentation for the particular variant for details).

4.2.11.5 ICD-X Filter Properties

No need for filters identified yet.

4.2.11.6 Implicit Value Sets

No need for implicit value sets identified yet.