title: Using empiric semantic correlation to interpret temporal assertions in clinical texts.
abstract: OBJECTIVE
  To measure the uncertainty of temporal assertions like "3 weeks ago" in clinical texts.
  
  
  METHODS
  Temporal assertions extracted from narrative clinical reports were compared to facts extracted from a structured clinical database for the same patients.
  
  
  METHODS
  The authors correlated the assertions and the facts to determine the dependence of the uncertainty of the assertions on the semantic and lexical properties of the assertions.
  
  
  RESULTS
  The observed deviation between the stated duration and actual duration averaged about 20% of the stated deviation. Linear regression revealed that assertions about events further in the past tend to be more uncertain, smaller numeric values tend to be more uncertain (1 mo v. 30 d), and round numbers tend to be more uncertain (10 versus 11 yrs).
  
  
  CONCLUSIONS
  The authors empirically derived semantics behind statements of duration using "ago," and verified intuitions about how numbers are used.
authors.affiliation: Department of Biomedical Informatics, Columbia University, College of Physicians and Surgeons, 622 West 168 Street, VC-5, New York, NY 10032, USA.
authors.forename: George
authors.initials: G
authors.lastname: Hripcsak
authors.forename: Noémie
authors.initials: N
authors.lastname: Elhadad
authors.forename: Yueh-Hsia
authors.initials: YH
authors.lastname: Chen
authors.forename: Li
authors.initials: L
authors.lastname: Zhou
authors.forename: Frances P
authors.initials: FP
authors.lastname: Morrison
mesh_terms: D006801:Humans; D016014:Linear Models; D008499:Medical Records; D009323:Natural Language Processing; D010351:Patient Discharge; D012660:Semantics; D013995:Time