[1][2] The primary purpose of SNOMED CT is to encode the meanings that are used in health information and to support the effective clinical recording of data with the aim of improving patient care.

SNOMED CT comprehensive coverage includes: clinical findings, symptoms, diagnoses, procedures, body structures, organisms and other etiologies, substances, pharmaceuticals, devices and specimens.

SNOMED CT provides for consistent information interchange and is fundamental to an interoperable electronic health record.

It provides a consistent means to index, store, retrieve, and aggregate clinical data across specialties and sites of care.

It also helps in organizing the content of electronic health records systems by reducing the variability in the way data are captured, encoded and used for clinical care of patients and research.

The availability of free automatic coding tools and services, which can return a ranked list of SNOMED CT descriptors to encode any clinical report, could help healthcare professionals to navigate the terminology.

[5] SNOMED started in 1965 as a Systematized Nomenclature of Pathology (SNOP) and was further developed into a logic-based health care terminology.

[9][10] The International Health Terminology Standards Development Organisation now considers SNOMED CT to be a brand name rather than an acronym.

SNOMED RT, with over 120,000 concepts, was designed to serve as a common reference terminology for the aggregation and retrieval of pathology health care data recorded by multiple organizations and individuals.

CTV3, with 200,000 interrelated concepts, was used for storing structured information about primary care encounters in individual, patient-based records.

[12] In July 2003, the National Library of Medicine (NLM), on behalf of the United States Department of Health and Human Services, entered into an agreement with the College of American Pathologists to make SNOMED CT available to U.S. users at no cost through the National Library of Medicine's Unified Medical Language System UMLS Metathesaurus.

[9][14][15] In April 2007, SNOMED CT intellectual property rights were transferred from the CAP to the International Health Terminology Standards Development Organisation (IHTSDO) in order to promote international adoption and use of SNOMED CT. Now trading as SNOMED International, the organization is responsible for "ongoing maintenance, development, quality assurance, and distribution of SNOMED CT" internationally[6][5][10] and its Membership consists of a number of the world's leading e-health countries and territories, including: Argentina, Australia, Belgium, Brunei, Canada, Czech Republic, Chile, Denmark, Estonia, Hong Kong, Iceland, India, Ireland, Israel, Lithuania, Malaysia, Malta, Netherlands, New Zealand, Norway, Poland, Portugal, Singapore, Slovak Republic, Republic of Slovenia, Spain, Sweden, Switzerland, United Kingdom, United States and Uruguay.

That is, all individual "cold-processes" are also included in all superclasses of the class Common Cold, such as Viral upper respiratory tract infection (Figure).

In contrast, the example Viral upper respiratory tract infection depicts a fully described concept, which is represented in description logic as follows: This means that each and every individual disorder for which all definitional criteria are met can be classified as an instance of Viral upper respiratory tract infection.

Major Electronic Health Record Systems (EHRS) have repeatedly complained to IHTSDO and other standards organizations about the "complexity" of post-coordinated expressions.

Prior 2020, International Classification of Diseases (ICD) did not allow post-coordination and SNOMED CT was the only terminology that supported postcoordination.

On the one hand, the necessity of post-coordination was perceived as a user-unfriendly obstacle, which has certainly contributed to the rather low adoption of early SNOMED versions.

However, the fusion with CTV3, as a historically grown terminology with many close-to user descriptions, introduced some problems which still affect SNOMED CT.

In addition to a confusing taxonomic web of many hierarchical levels with massive multiple inheritance (e.g. there are 36 taxonomic ancestors for Acute appendicitis), many ambiguous, context-dependent concepts have found their way into SNOMED CT. Pre-coordination was sometimes pushed to extremes, so there are, for example, 350 different concepts for burns found on the head.

[23] Human language is misleading here, as we use syntactically similar expression to represent categorically distinct entities, e.g. Ectopic pregnancy vs.

A major reason for why such concepts cannot be dispensed with is that SNOMED CT takes on, in many cases, the functionality of information models, as the latter do not exist in a given implementation.

Criticism of the state of the terminology was sparked by numerous substantive weaknesses as well as on the lack of quality assurance measures.

The increased take-up of SNOMED CT for research into applications in daily use across the world to support patient care is leading to a larger engaged community.

This is leading to an increase in the number of software tools and development of materials that contribute to knowledge base to support implementation.

However, partly as the continuing fall-out from the merger with CTV3, SNOMED still contains undiscovered semantically duplicate primitive and defined concepts.

[29] The International Statistical Classification of Diseases and Related Health Problems (ICD) is an internationally used medical classification system; which is used to assign diagnostic and, in some national modifications, procedural codes in order to produce coded data for statistical analysis, epidemiology, reimbursement and resource allocation.

There are two types of license: For scientific research in medical informatics, for demonstrations or evaluation purposes SNOMED CT sources can be freely downloaded and used.

The original SNOMED CT sources in tabular form are accessible by registered users of the Unified Medical Language System (UMLS) who have signed an agreement.

Those wishing to obtain a license for its use and to download SNOMED CT should contact their National Release Centre, links to which are provided on the IHTSDO website.

For example, a set of 7 314 codes and descriptions is free for use by users of DICOM-compliant software (without restriction to IHTSDO member countries).