title: Assessing thesaurus-based query expansion using the UMLS Metathesaurus.
abstract: OBJECTIVE
  Assess query expansion using thesaurus relationships and definitions in the UMLS Metathesaurus for improving searching performance.
  
  
  METHODS
  The queries from a MEDLINE test collection (OHSUMED) were expanded using synonym, hierarchical, and related term information as well as term definitions from the UMLS Metathesaurus. Documents were retrieved from a word-statistical retrieval system and assessed for recall and precision based on relevance judgments from the test collection.
  
  
  RESULTS
  All types of query expansion degraded aggregate retrieval performance as measured by recall and precision, although 38.6% of the queries with synonym expansion and up to 29.7% of the queries with hierarchical expansion showed improvement.
  
  
  CONCLUSIONS
  Thesaurus-based query expansion causes a decline in retrieval performance generally but improves it in specific instances. Further research must focus on identifying instances where performance improves and how it can be exploited by real users.
authors.affiliation: Division of Medical Informatics & Outcomes Research, Oregon Health Sciences University, Portland, Oregon, USA.
authors.forename: W
authors.initials: W
authors.lastname: Hersh
authors.forename: S
authors.initials: S
authors.lastname: Price
authors.forename: L
authors.initials: L
authors.lastname: Donohoe
mesh_terms: D016247:Information Storage and Retrieval / Q000379:methods*; D016239:MEDLINE; D017432:Unified Medical Language System; D018875:Vocabulary, Controlled