This mapping is a tabular, knowledge-based cross-link from SNOMED CT to ICD-10 in which the most accurate ICD-10 target code or codes that best represents the SNOMED CT concept are linked. The ICD-10 map is a link directed from the source SNOMED CT concept to the target ICD-10 statistical classification.

Map relationships

The granularity and purpose of ICD-10 is different from that of SNOMED CT. 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 distinct from all other concepts. SNOMED CT supports a model of meaning which specifies correct attributes and value sets for each domain of meaning.

ICD-10 is a classification of diseases and related health problems with granularity of definition that has been chosen to provide utility for purposes of epidemiology and statistical reporting of 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.

Only domains of SNOMED CT which overlap in meaning with those of ICD-10 will be mapped. Due to differences in granularity, purpose and rubrics, assignment of a mapping equivalence between the SNOMED CT source and ICD-10 target code is usually not appropriate. Instead, the ICD-10 map will link a SNOMED CT source concept to the ICD-10 code which contains the meaning of the SNOMED CT concept as conceptualized by ICD-10.

All pre-coordinated concepts issued by SNOMED International within the current international release of SNOMED CT with active status within the following SNOMED CT domains may be mapped:

• Clinical finding (disorders and findings) Concept.id 404684003 and descendants
• Event Concept.id 272379006 and descendants
• Situation with explicit context Concept.id 243796009 and descendants

Target domain context and scope

All chapters of ICD-10 are considered within scope for this ICD-10 map. The Morphology of Neoplasms, which is a nomenclature of codes designed for use in conjunction with Chapter 11 Neoplasms, is out of scope for this ICD-10 map.

The scope of ICD-10 is described in WHO's Volume 2 as follows: "The ICD-10 is primarily designed for the classification of diseases and injuries designated as a formal diagnosis. ICD-10 also classifies signs, symptoms, abnormal findings, complaints, and social circumstances that may appear in a health record. Thus ICD-10 is used to classify data recorded under headings such as 'diagnosis', 'reason for admission', 'conditions treated', and 'reason for consultation'."

Many SNOMED CT concepts within the source domains may be normal findings or other concepts not intended for classification by ICD-10. See Exemplar: NotClassifiable, #1-19 for examples. Throughout the rest of this document, exemplar references will be abbreviated "Exemplar: [reference to the specific worksheet], [reference to the numbers for the example(s)].

Mapping Cardinality

The ICD-10 map has cardinality of one SNOMED CT source concept to zero-to-many ICD-10 classification codes. Zero target codes are appropriate if the source concept is not classifiable or is awaiting editorial review for guidance. In all other cases, one or more map targets will be assigned. This is usually no more than three. One or more Map members will be required for the knowledge-based mapping to each ICD-10 classification code target. These Map members will be coordinated in mapGroups each yielding at most one target.