title: The COSMIN study reached international consensus on taxonomy, terminology, and definitions of measurement properties for health-related patient-reported outcomes.
abstract: OBJECTIVE
  Lack of consensus on taxonomy, terminology, and definitions has led to confusion about which measurement properties are relevant and which concepts they represent. The aim was to clarify and standardize terminology and definitions of measurement properties by reaching consensus among a group of experts and to develop a taxonomy of measurement properties relevant for evaluating health instruments.
  
  
  METHODS
  An international Delphi study with four written rounds was performed. Participating experts had a background in epidemiology, statistics, psychology, and clinical medicine. The panel was asked to rate their (dis)agreement about proposals on a five-point scale. Consensus was considered to be reached when at least 67% of the panel agreed.
  
  
  RESULTS
  Of 91 invited experts, 57 agreed to participate and 43 actually participated. Consensus was reached on positions of measurement properties in the taxonomy (68-84%), terminology (74-88%, except for structural validity [56%]), and definitions of measurement properties (68-88%). The panel extensively discussed the positions of internal consistency and responsiveness in the taxonomy, the terms "reliability" and "structural validity," and the definitions of internal consistency and reliability.
  
  
  CONCLUSIONS
  Consensus on taxonomy, terminology, and definitions of measurement properties was reached. Hopefully, this will lead to a more uniform use of terms and definitions in the literature on measurement properties.
authors.affiliation: Department of Epidemiology and Biostatistics, The EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands. w.mokkink@vumc.nl
authors.forename: Lidwine B
authors.initials: LB
authors.lastname: Mokkink
authors.forename: Caroline B
authors.initials: CB
authors.lastname: Terwee
authors.forename: Donald L
authors.initials: DL
authors.lastname: Patrick
authors.forename: Jordi
authors.initials: J
authors.lastname: Alonso
authors.forename: Paul W
authors.initials: PW
authors.lastname: Stratford
authors.forename: Dirk L
authors.initials: DL
authors.lastname: Knol
authors.forename: Lex M
authors.initials: LM
authors.lastname: Bouter
authors.forename: Henrica C W
authors.initials: HC
authors.lastname: de Vet
mesh_terms: D002985:Clinical Protocols / Q000145:classification / Q000592:standards*; D032921:Consensus; D003627:Data Interpretation, Statistical; D003697:Delphi Technique; D017408:Guidelines as Topic; D006304:Health Status; D006305:Health Status Indicators; D006801:Humans; D007391:International Cooperation; D017063:Outcome Assessment, Health Care / Q000145:classification / Q000592:standards*; D011594:Psychometrics; D011788:Quality of Life; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D009626:Terminology as Topic