title: Decisions about lumping vs. splitting of the scope of systematic reviews of complex interventions are not well justified: a case study in systematic reviews of health care professional reminders.
abstract: OBJECTIVE
  Lumping and splitting refer to the scope of a systematic review question, where lumped reviews are broad and split are narrow. The objective was to determine the frequency of lumping and splitting in systematic reviews of reminder interventions, assess how review authors justified their decisions about the scope of their reviews, and explore how review authors cited other systematic reviews in the field.
  
  
  METHODS
  A descriptive approach involving a content analysis and citation bibliometric study of an overview of 31 systematic reviews of reminder interventions.
  
  
  RESULTS
  Twenty-four of 31 reminder reviews were split, most frequently across one category (population, intervention, study design, outcome). Review authors poorly justified their decisions about the scope of their reviews and tended not to cite other similar reviews.
  
  
  CONCLUSIONS
  This study demonstrates that for systematic reviews of reminder interventions, splitting is more common than lumping, with most reviews split by condition or targeted behavior. Review authors poorly justify the need for their review and do not cite relevant literature to put their reviews in the context of the available evidence. These factors may have contributed to a proliferation of systematic reviews of reminders and an overall disorganization of the literature.
authors.affiliation: University of Toronto, Faculty of Medicine, Toronto, ON, Canada.
authors.forename: Michelle C
authors.initials: MC
authors.lastname: Weir
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Grimshaw
authors.forename: Alain
authors.initials: A
authors.lastname: Mayhew
authors.forename: Dean
authors.initials: D
authors.lastname: Fergusson
mesh_terms: D000465:Algorithms; D015706:Bibliometrics; D003657:Decision Making; D019317:Evidence-Based Medicine; D006801:Humans; D012107:Research Design; D012196:Review Literature as Topic