title: What is an evidence map? A systematic review of published evidence maps and their definitions, methods, and products.
abstract: BACKGROUND
  The need for systematic methods for reviewing evidence is continuously increasing. Evidence mapping is one emerging method. There are no authoritative recommendations for what constitutes an evidence map or what methods should be used, and anecdotal evidence suggests heterogeneity in both. Our objectives are to identify published evidence maps and to compare and contrast the presented definitions of evidence mapping, the domains used to classify data in evidence maps, and the form the evidence map takes.
  
  
  METHODS
  We conducted a systematic review of publications that presented results with a process termed "evidence mapping" or included a figure called an "evidence map." We identified publications from searches of ten databases through 8/21/2015, reference mining, and consulting topic experts. We abstracted the research question, the unit of analysis, the search methods and search period covered, and the country of origin. Data were narratively synthesized.
  
  
  RESULTS
  Thirty-nine publications met inclusion criteria. Published evidence maps varied in their definition and the form of the evidence map. Of the 31 definitions provided, 67 % described the purpose as identification of gaps and 58 % referenced a stakeholder engagement process or user-friendly product. All evidence maps explicitly used a systematic approach to evidence synthesis. Twenty-six publications referred to a figure or table explicitly called an "evidence map," eight referred to an online database as the evidence map, and five stated they used a mapping methodology but did not present a visual depiction of the evidence.
  
  
  CONCLUSIONS
  The principal conclusion of our evaluation of studies that call themselves "evidence maps" is that the implied definition of what constitutes an evidence map is a systematic search of a broad field to identify gaps in knowledge and/or future research needs that presents results in a user-friendly format, often a visual figure or graph, or a searchable database. Foundational work is needed to better standardize the methods and products of an evidence map so that researchers and policymakers will know what to expect of this new type of evidence review.
  
  
  BACKGROUND
  Although an a priori protocol was developed, no registration was completed; this review did not fit the PROSPERO format.
authors: Evidence-based Synthesis Program (ESP) Center, Veterans Affairs Greater Los Angeles Healthcare System, 11301 Wilshire Blvd, Los Angeles, CA, 90073, USA. isomi.miake-lye@va.gov.|Department of Health Policy and Management, Fielding School of Public Health, University of California, Los Angeles, 640 Charles E Young Dr S, Los Angeles, CA, USA. isomi.miake-lye@va.gov.
authors: Isomi M
authors: IM
authors: Miake-Lye
authors: Southern California Evidence-based Practice Center, RAND Corporation, 1776 Main St, Santa Monica, CA, 90401, USA.
authors: Susanne
authors: S
authors: Hempel
authors: Southern California Evidence-based Practice Center, RAND Corporation, 1776 Main St, Santa Monica, CA, 90401, USA.
authors: Roberta
authors: R
authors: Shanman
authors: Evidence-based Synthesis Program (ESP) Center, Veterans Affairs Greater Los Angeles Healthcare System, 11301 Wilshire Blvd, Los Angeles, CA, 90073, USA.|Southern California Evidence-based Practice Center, RAND Corporation, 1776 Main St, Santa Monica, CA, 90401, USA.|Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, 10833 Le Conte Ave, Los Angeles, CA, 90095, USA.
authors: Paul G
authors: PG
authors: Shekelle
mesh_terms: D006801:Humans; D012196:Review Literature as Topic