# Scope and Procedures

The map is a tabular, knowledge-based cross-link from SNOMED CT to ICD-10. It contains a set of directed relationships from a source SNOMED CT concept to one or more target ICD-10 codes that most accurately describe the meaning of the SNOMED CT concept.

## Map relationships

ICD-10 and SNOMED CT are intended to serve different, yet complementary, purposes.

{% columns %}
{% column %}
**SNOMED CT** is a comprehensive reference terminology that supports both general and highly specific concepts. Each concept is defined by a set of attribute-value pairs (relationships) which uniquely define it as distinct from all other concepts. SNOMED CT supports a model of meaning which specifies correct attributes and value sets for each domain of meaning.
{% endcolumn %}

{% column %}
**ICD-10** is a statistical classification of diseases and related health problems with a granularity of definition that has been chosen to provide utility for purposes of epidemiological and statistical reporting of both mortality and morbidity. ICD-10 was created to classify a clinical concept by defining the classes (or 'buckets' of meaning) which contain the concept within the universe of ICD-10 classes.
{% endcolumn %}
{% endcolumns %}

Due to the differences in the fidelity of these information representations, a map correlation ID between the SNOMED CT source and ICD-10 target code is usually not appropriate. Instead, the map will link the SNOMED CT source concept to the ICD-10 target code that expresses the same meaning of the concept as conceptualized by ICD-10.

## Target domain context and scope

The map only includes SNOMED concepts from those top-level hierarchies that overlap with the domains represented in ICD-10. These are:

* Clinical finding, including disorders
* Event
* Situation with explicit context

{% hint style="success" %}
Only pre-coordinated concepts published in the current release of the SNOMED CT International Edition with an active status will be considered in scope of the map.
{% endhint %}

All chapters of ICD-10 are considered to be in scope for mapping. The Morphology of Neoplasms – which is a nomenclature of codes designed for use in conjunction with Chapter II Neoplasms – is excluded.

ICD-10 has been designed primarily for the classification of diseases and injuries as a formal diagnosis. However, as stated in the ICD-10 Instruction Manual, it also:

> *provides for a wide variety of signs, symptoms, abnormal findings, complaints and social circumstances that may stand in place of a diagnosis on health-related records. It can therefore be used to classify data recorded under headings such as ‘diagnosis’, ‘reason for admission’, ‘conditions treated’ and ‘reason for consultation’, which appear on a wide variety of health records from which statistics and other health-situation information are derived.*

<p align="right"><em>ICD-10 Fifth Edition (2016), Volume II: Instruction Manual, p 3</em></p>

## Mapping Cardinality

The map cardinality shall be one SNOMED CT source concept to zero or more (0:\*) ICD-10. Zero target codes are appropriate in situations where the source concept cannot be classified with the available information. Examples include ICD demanding greater specificity than is available in the source, or the concept describes a circumstance outside the scope of the classification.

{% hint style="danger" %}
Many SNOMED CT concepts within the Clinical finding hierarchy represent normal findings or states that are not intended for classification by ICD-10. Such concepts will be recorded as 'Not classifiable'.
{% endhint %}

One or more map members will be required for the knowledge-based mapping to each ICD-10 classification code target. Where more than one target code is needed to fully express the meaning of a concept, these codes, or map members, will be coordinated using mapGroups[^1].

<a href="https://docs.google.com/forms/d/e/1FAIpQLScTmbZIf0UEQwYDkY27EEWBkaiYkHSbR0_9DmFrMLXoQLyL7Q/viewform?usp=pp_url&#x26;entry.1767247133=ICD-10+Map+Specification&#x26;entry.670899847=Scope%20and%20Procedures" class="button primary">Provide Feedback</a>

[^1]: Groups a set of complex map records from which one may be selected as a target code. Where a SNOMED CT concept maps onto multiple target codes, there will be multiple groups, each containing one or more complex map records.


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