title: Identifying phases of investigation helps planning, appraising, and applying the results of explanatory prognosis studies.
abstract: OBJECTIVE
  To present an explanatory framework for understanding prognosis and illustrate it using data from a systematic review.
  
  
  METHODS
  A framework including three phases of explanatory prognosis investigation was adapted from earlier work and a discussion of causal understanding was integrated. For illustration, prognosis studies were identified from electronic and supplemental searches of literature between 1966 and December 2006. We extracted characteristics of the populations, exposures, and outcomes and identified three phases of explanatory prognosis investigation: Phase 1, identifying associations; Phase 2, testing independent associations; and Phase 3, understanding prognostic pathways. The purpose of each phase is exploration, confirmation, and development of understanding, respectively.
  
  
  RESULTS
  It is important to consider a framework of explanatory prognosis studies for: (1) defining the study objectives, (2) presenting the study methods and data, and (3) interpreting and applying the results of the study.
  
  
  CONCLUSIONS
  When conducting and reporting prognosis studies, researchers should consider the approach to prognosis (explanatory or outcome prediction) and phase of investigation, use best methods to limit biases, report completely, and cautiously interpret results. Readers of health care research will then be better able to evaluate the goals and interpret and appropriately use the results of prognosis studies.
authors.affiliation: Centre for Research Expertise In Disability Outcomes, University Health Network Rehabilitation Solutions, Toronto, Canada. jhayden@uhnresearch.ca
authors.forename: J A
authors.initials: JA
authors.lastname: Hayden
authors.forename: P
authors.initials: P
authors.lastname: Côté
authors.forename: I A
authors.initials: IA
authors.lastname: Steenstra
authors.forename: C
authors.initials: C
authors.lastname: Bombardier
mesh_terms: D015984:Causality; D004185:Disability Evaluation; D006302:Health Services Research / Q000379:methods; D006801:Humans; D016365:Liability, Legal; D017116:Low Back Pain / Q000534:rehabilitation; D017063:Outcome Assessment, Health Care / Q000379:methods*; D011379:Prognosis; D012107:Research Design; D012196:Review Literature as Topic