title: The use of comorbidities among adults experiencing care transitions: a systematic review and evolutionary analysis of empirical literature.
abstract: OBJECTIVE
  To systematically review how comorbidities are employed in the empirical literature for adults coping with multiple chronic conditions during common episodes of acute illness that resulted in transition across health care setting.
  
  
  METHODS
  Evolutionary concept analysis inductively identifies current consensus regarding the usage of a concept and results in exploring attributes and clarification of the concept. Sixty studies from 1965 to 2009 identified from MEDLINE, CINAHL, PsychINFO, and ISI Web of Science databases were analysed.
  
  
  RESULTS
  Comorbidities were used heterogeneously among reviewed studies with most controlling for their presence (n=33) and lacking robust measurement (n=37). The designation of index or principal condition was equally heterogeneous with approximately half (n=26) representing the main disease or diagnosis of interest to the researcher. In this study comorbidities were associated with personal, disease or system level antecedents and consequences. A conceptual framework is proposed.
  
  
  CONCLUSIONS
  The impact of comorbidities on the care and outcomes of adults coping with multiple chronic conditions is limited by heterogeneous and ambiguous usage. While analytic techniques have become more sophisticated, continued lack of meaningful conceptualization and instrument use has limited maturation of this important concept for research, practice and policy purposes.
authors.affiliation: School of Nursing, The Pennsylvania State University, University Park, Philadelphia, 16802, USA. hgb2@psu.edu
authors.forename: Harleah G
authors.initials: HG
authors.lastname: Buck
authors.forename: Salimah
authors.initials: S
authors.lastname: Meghani
authors.forename: Janet Prvu
authors.initials: JP
authors.lastname: Bettger
authors.forename: Eeeseung
authors.initials: E
authors.lastname: Byun
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Fachko
authors.forename: Melissa
authors.initials: M
authors.lastname: O'Connor
authors.forename: Christine
authors.initials: C
authors.lastname: Tocchi
authors.forename: Mary
authors.initials: M
authors.lastname: Naylor
mesh_terms: D000328:Adult; D002908:Chronic Disease / Q000453:epidemiology* / Q000628:therapy*; D015897:Comorbidity; D003695:Delivery of Health Care; D006801:Humans; D016896:Treatment Outcome