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Representation of clinical laboratory terminology in the Unified Medical Language System.

The Unified Medical Language System (UMLS) was examined to determine its coverage of clinical laboratory terminology in use at the Columbia-Presbyterian Medical Center (CPMC). The Metathesaurus (Meta-1) contains exact matches for 30% of 1460 CPMC laboratory terms and near matches for an additional 42%, with better coverage of atomic-level concepts ("substance" terms) than complex ones (tests and panels). The Semantic Network includes types for representing laboratory procedures (2), measured substances (at least 56) and sampled substances (at least 14), but no type to represent specimens. Few of the UMLS semantic relationships are applicable to the CPMC vocabulary. These results have implications for the utility of the UMLS for linking clinical databases to electronic medical information sources.

Clinical Laboratory Techniques↗

From French vocabulary to the Unified Medical Language System: a preliminary study.

The Unified Medical Language System (UMLS) is an extensive source of biomedical knowledge developed and maintained by the U.S. National Library of Medicine (NLM). The UMLS began to include biomedical terms in other languages a few years ago. However, providing foreign terms for existing concepts is only the first step for the UMLS to become international. The current limits of the use of the UMLS in French are analyzed (partial translation, unique source of the translated concepts, improper character set, and absence of lexical resources for lexical matching tools). Some suggestions are given for French to be better integrated into the UMLS, especially for adapting the lexical resources to French. Once completed, our present work is expected to give the UMLS the capability to be effectively queried in French.

France↗

Automatic enrichment of the unified medical language system starting from the ADM knowledge base.

The Unified Medical Language System (UMLS) project aims to provide a repository of terms, concepts and relationships from several medical classifications. This work describes the possibility to enrich automatically with meaningful links the UMLS database by using description of diseases from another knowledge base, in our case ADM (Aide au Diagnostic Medical). In spite of the constraints and the difficulties to qualify the interconcept links, the results show that it is possible to find and create new links from a french knowledge database to the UMLS one. One of the interests of this work is that the automated learning of the connections could be used with others knowledge databases like expert system databases.

Algorithms↗

Mapping medical vocabularies to the Unified Medical Language System.

This paper presents our work in automated mapping of medical vocabularies to the National Library of Medicine's Unified Medical Language System (UMLS). We used the UMLS Knowledge Source (KS) tool to map terms from several sources to UMLS Metathesaurus concepts. We compared performance of the KS tools with our own Minimal Representable Units Method (MRUM). The KS tools were able to map terms from 13% to 54% of the time, depending on the term set and the KS options used. Our MRUM method mapped between 96% and 99% of the terms. Based on our experience, we believe that questions remain about the best method by which the UMLS can be used to achieve automated term translation.

Algorithms↗

UMLS-based access to CPR data. Unified Medical Language Systems.

This paper describes the results of a project that explores the use the Unified Medical Language System (UMLS) for knowledge-driven tasks, such as browsing a computer-based patient record (CPR). The project consisted of a number of steps: the mapping between CPR terms and UMLS concepts, the development of an algorithm that explores the CPR data using this mapping and the implementation of a first prototype browser that visualizes 'found' data. A second task addressed in this project has been the direct access to online medical literature (MEDLINE) using the UMLS concepts found in the CPR data. In this project, we used a preliminary version of the Open Records for Patient Care (ORCA) CPR that consisted only of the history and physical examination data of patient suffering from heart failure.

Algorithms↗

Auditing the Unified Medical Language System with semantic methods.

OBJECTIVE: The National Library of Medicine's (NLM) Unified Medical Language System (UMLS) includes a Metathesaurus (Meta), which is a compilation of medical terms drawn from over 30 controlled vocabularies, and a Semantic Net, which contains the semantic types used to categorize Meta concepts and the semantic relations to connect them. Meta has been constructed through lexical matching techniques and human review. The purpose of this study was to audit the Meta using semantic techniques to identify possible inconsistencies. METHODS: Five different techniques were applied: (1) detection of ambiguity in Meta concepts with two or more semantic types, (2) detection of interchangeable keyword synonyms, (3) detection of redundant pairs of Meta concepts (using lexical matching combined with keyword synonyms), (4) detection of inconsistent parent-child relationships in Meta (based on the semantic type information), and (5) discovery of pairs of semantic types for which relations could be added to the Semantic Net, based on "other" relationships between Meta concepts. RESULTS: Of 57,592 concepts with multiple semantic types, 1817 (3.2%) were judged to be ambiguous. Keyword analysis showed 7121 pairs of interchangeable words. Using the keyword pairs, 5031 pairs of potentially redundant concepts were suggested, of which 3274 (65.1%) were judged to actually be redundant. Review of the 100,586 parent-child relationships revealed 544 (0.54%) that were incorrect. Review of the 219,664 "Other" relationships suggested 1299 places in the Semantic Net where relations between pairs of semantic types could be added. CONCLUSION: Semantic techniques, alone or in combination, can be used to audit the UMLS to detect inconsistencies that are not detectable through lexical techniques alone. Use of these methods to augment the UMLS maintenance process will lead to improvement in the UMLS.

Algorithms↗

The Unified Medical Language System: toward a collaborative approach for solving terminologic problems.

The approach taken by the Unified Medical Language System (UMLS), in which disparate terminology systems are integrated, has allowed construction of an electronic thesaurus (the Metathesaurus) that avoids imposing any restrictions upon the content, structure, or semantics of the source terminologies. As such, the UMLS has served as a unifying paradigm by providing appropriate links among equivalent entities that are used in different contexts or for different purposes. It accordingly provides a vehicle through which possibly orthogonal semantic models can co-exist within a single framework. This framework provides a model for the collaborative evolution of biomedical terminology and allows a synergistic relationship between the UMLS and its source terminology systems.

Systems Integration↗

Use of the Unified Medical Language System in patient care at the Columbia-Presbyterian Medical Center.

The Unified Medical Language System (UMLS) project at the United States National Library of Medicine contains and organizes a large number of terms from controlled medical vocabularies. This study examines the suitability of the UMLS for representing patient care information as it exists in the Columbia-Presbyterian Medical Center (CPMC) clinical information system. Comparisons were made between the semantic types, semantic relations and medical concepts of the UMLS and the data model entities, semantic classes, semantic relations and concepts in the CPMC system. Results of the comparison demonstrate that the UMLS structural model is appropriate for representing CPMC vocabularies and patient data and that the UMLS concepts provide excellent coverage of CPMC concepts in many areas. Recommendations are made for enhancing UMLS structure to provide additional coverage of the CPMC model. It is concluded that content expansion to provide better coverage of clinical terminology is possible within the current UMLS model.

Academic Medical Centers↗

The rubber meets the road: integrating the Unified Medical Language System Knowledge Source Server into the computer-based patient record.

Ongoing improvements in the content of the Unified Medical Language System, coupled with the recent release of the Internet-based Knowledge Source Server (KSS), have prompted us to develop an interface between the KSS and our computer-based patient record. We confronted many challenges while developing a robust interface to an Internet-based server, and in integrating the process of codification into the workflow of clinicians. An initial evaluation of the interface in the clinical environment suggests that acceptable performance is attainable. The benefits of using an Internet-accessible tool in a clinical information system appear to justify the effort required.

Humans↗

Acceptability of Unified Medical Language System terms as substitute for natural language general medicine clinic diagnoses.

The acceptability of using the Unified Medical Language System (UMLS) concept phrases to substitute for physicians' diagnosis statements was investigated. Physician diagnosis statements recorded in the University of New Mexico's General Medicine Clinic were input into a computer program that automatically finds the best matching UMLS concept phrases. The computer program written in C++ integrates UMLS searching and browsing with a graphical user interface. Five attending physicians in the Department of Internal Medicine rated the acceptability of the UMLS concept phrase as a substitute for the original physician statement. One hundred and ninety-five patients' notes were examined with 447 diagnosis statements recorded of which 271 statements were unique. Attending physicians rated their satisfaction with the automated UMLS substitutes on a scale of 1 (extremely dissatisfied) to 5 (extremely satisfied). Intrarater (mean 0.94) and interrater correlations (mean 0.75) were high. The mean rating was 4.0 (quite satisfied). Most (73%) of the substitution were satisfactory (rating of 4 or 5), 16% were neutral (rating of 3), and 21% were unsatisfactory (rating of 1 or 2). A review of the substitutions showed a frequent lack of clinical modifier terms in UMLS as has been previously described. Comparison to a previous study shows the broader term coverage of UMLS to be a more acceptable source of diagnosis codes than using International Classification of Diseases revision 9 alone. These results suggest that UMLS can be an effective tool for coding unconstrained physician diagnoses.

Consumer Behavior↗

The Unified Medical Language System: an informatics research collaboration.

In 1986, the National Library of Medicine (NLM) assembled a large multidisciplinary, multisite team to work on the Unified Medical Language System (UMLS), a collaborative research project aimed at reducing fundamental barriers to the application of computers to medicine. Beyond its tangible products, the UMLS Knowledge Sources, and its influence on the field of informatics, the UMLS project is an interesting case study in collaborative research and development. It illustrates the strengths and challenges of substantive collaboration among widely distributed research groups. Over the past decade, advances in computing and communications have minimized the technical difficulties associated with UMLS collaboration and also facilitated the development, dissemination, and use of the UMLS Knowledge Sources. The spread of the World Wide Web has increased the visibility of the information access problems caused by multiple vocabularies and many information sources which are the focus of UMLS work. The time is propitious for building on UMLS accomplishments and making more progress on the informatics research issues first highlighted by the UMLS project more than 10 years ago.

Computer Communication Networks↗

Knowledge acquisition to qualify Unified Medical Language System interconceptual relationships.

Adding automatically relations between concepts from a database to a knowledge base such as the Unified Medical Language System can be very useful to increase the consistency of the latter one. But the transfer of qualified relationships is more interesting. The most important interest of these new acquisitions is that the UMLS became more compliant and medically pertinent to be used in different medical applications. This paper describes the possibility to inherit automatically medical inter-conceptual relationships qualifiers from a disease description included into a database and to integrate them into the UMLS knowledge base. The paper focuses on the transmission of knowledge from a French medical database to an English one.

Artificial Intelligence↗

Evaluation of the Unified Medical Language System as a medical knowledge source.

OBJECTIVE: The authors evaluated the use of the Unified Medical Language System (UMLS) as a medical knowledge source for the representation of medical procedures in the MAOUSSC system. DESIGN: MAOUSSC, a multiaxial coding system, was used for the representation of 1500 procedures from 15 clinical specialties, using UMLS concepts (augmented by full sources for three new vocabularies being added to the UMLS) and relationships whenever possible. Evaluation criteria for the UMLS included (1) completeness of representation of concepts and of inter-concept relationships, (2) consistency in the categorization of both concepts and inter-concept relationships, and (3) usability, including adaptability of the UMLS to a foreign language (French), its suitability to a geographic region with different medical practices than the USA, and issues relative to the annual update changes in the test vocabularies. RESULTS: During the MAOUSSC trial, the number of missing concepts or relationships identified in the augmented UMLS sources was deemed to be inconsequential relative to overall project goals. "Missing" UMLS inter-concept relationships were identified, although they were small in number. Some inconsistencies in the UMLS were noted, especially in the area of hierarchic relationships. CONCLUSION: After UMLS was used for five years as a knowledge source for representing 1500 complex medical procedures in MAOUSSC, its value is considered significant. Future editions of the UMLS are expected to improve representation of inter-concept relationships and global consistency.

Language↗

The Unified Medical Language System.

In 1986, the National Library of Medicine began a long-term research and development project to build the Unified Medical Language System (UMLS). The purpose of the UMLS is to improve the ability of computer programs to "understand" the biomedical meaning in user inquiries and to use this understanding to retrieve and integrate relevant machine-readable information for users. Underlying the UMLS effort is the assumption that timely access to accurate and up-to-date information will improve decision making and ultimately the quality of patient care and research. The development of the UMLS is a distributed national experiment with a strong element of international collaboration. The general strategy is to develop UMLS components through a series of successive approximations of the capabilities ultimately desired. Three experimental Knowledge Sources, the Metathesaurus, the Semantic Network, and the Information Sources Map have been developed and are distributed annually to interested researchers, many of whom have tested and evaluated them in a range of applications. The UMLS project and current developments in high-speed, high-capacity international networks are converging in ways that have great potential for enhancing access to biomedical information.

Information Storage and Retrieval↗

UMLS-based conceptual queries to biomedical information databases: an overview of the project ARIANE. Unified Medical Language System.

OBJECTIVE: The aim of the project ARIANE is to model and implement seamless, natural, and easy-to-use interfaces with various kinds of heterogeneous biomedical information databases. DESIGN: A conceptual model of some of the Unified Medical Language System (UMLS) knowledge sources has been developed to help end users to query information databases. A query is represented by a conceptual graph that translates the deep structure of an end-user's interest in a topic. A computational model exploits this conceptual model to build a query interactively represented as query graph. A query graph is then matched to the data graph built with data issued from each record of a database by means of a pattern-matching (projection) rule that applies to conceptual graphs. RESULTS: Prototypes have been implemented to test the feasibility of the model with different kinds of information databases. Three cases are studied: 1) information in records is structured according to the UMLS knowledge sources; 2) information is able to be structured without error in the frame of the UMLS knowledge; 3) information cannot be structured. In each case the pattern-matching is processed by the projection rule according to the structure of information that has been implemented in the databases. CONCLUSION: The conceptual graphs theory provides with a homogeneous and powerful formalism able to represent both concepts, instances of concepts in medical contexts, and associations by means of relationships, and to represent data at different levels of details. The conceptual-graphs formalism allows powerful capabilities to operate a semantic integration of information databases using the UMLS knowledge sources.

Databases as Topic↗

Knowledge representation and indexing using the unified medical language system.

Ontologies and semantic frameworks can be used to improve the accuracy and expressiveness of natural language processing for the purpose of extracting meaning from technical documents. This is especially true when a rich ontology such as the Unified Medical Language System (UMLS) is available. This paper reports on some tools being developed to make this possible and on some experience with a user interface based on ontologies and semantic networks that allows for interactive knowledge exploration.

Abstracting and Indexing↗