title: Using concept hierarchies to improve calculation of patient similarity.
abstract: We introduce a new distance measure that is better suited than traditional methods at detecting similarities in patient records by referring to a concept hierarchy.
  
  
  
  The new distance measure improves on distance measures for categorical values by taking the path distance between concepts in a hierarchy into account. We evaluate and compare the new measure on a data set of 836 patients.
  
  
  
  The new measure shows marked improvements over the standard measures, both qualitatively and quantitatively. Using the new measure for clustering patient data reveals structure that is otherwise not visible. Statistical comparisons of distances within patient groups with similar diagnoses shows that the new measure is significantly better at detecting these similarities than the standard measures.
  
  
  
  The new distance measure is an improvement over the current standard whenever a hierarchical arrangement of categorical values is available.
authors.affiliation: RISC Software GmbH, Research Unit Medical Informatics, Johannes Kepler University Linz/Hagenberg, Austria.
authors.forename: Dominic
authors.initials: D
authors.lastname: Girardi
authors.affiliation: RISC Software GmbH, Research Unit Medical Informatics, Johannes Kepler University Linz/Hagenberg, Austria.
authors.forename: Sandra
authors.initials: S
authors.lastname: Wartner
authors.affiliation: Department of Process Management in Health Care, University of Applied Sciences Upper Austria, Steyr, Austria.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Halmerbauer
authors.affiliation: Department of Process Management in Health Care, University of Applied Sciences Upper Austria, Steyr, Austria.
authors.forename: Margit
authors.initials: M
authors.lastname: Ehrenmüller
authors.affiliation: Institute for Application Oriented Knowledge Processing, Johannes Kepler University Linz, Austria.
authors.forename: Hilda
authors.initials: H
authors.lastname: Kosorus
authors.affiliation: Department of Software Engineering, University of Applied Sciences Upper Austria, Hagenberg, Austria. Electronic address: stephan.dreiseitl@fh-hagenberg.at.
authors.forename: Stephan
authors.initials: S
authors.lastname: Dreiseitl
mesh_terms: D000465:Algorithms; D016000:Cluster Analysis; D057286:Electronic Health Records; D006801:Humans; D010361:Patients / Q000145:classification*
keywords: Distance measure using concept hierarchy; ICD-10 taxonomy; Patient similarity calculation