title: Validation of a consensus-based minimal clinically important difference (MCID) threshold using an objective functional external anchor.
abstract: BACKGROUND
  The minimal clinically important difference (MCID) is defined as the smallest change in an outcome that a patient would perceive as meaningful. The Initiative on Methods, Measurement and Assessment in Clinical Trials (IMMPACT) group proposed defining the MCID as a 30% improvement in self-reported pain or function. However, this MCID threshold has not been validated against an objective physical measure.
  
  
  OBJECTIVE
  To test the validity of the IMMPACT-based MCID threshold, using an objective physical measure as an external anchor.
  
  
  METHODS
  Prospective study of chronic disabling occupational lumbar disorder (CDOLD) patients completing a functional restoration program.
  
  
  METHODS
  A consecutive cohort of 743 CDOLD patients.
  
  
  METHODS
  Self-report measures of pain-related function were compared with an objective lifting measure, the progressive isoinertial lifting evaluation (PILE), obtained after treatment.
  
  
  METHODS
  The association between reporting 30% or greater improvement (the IMMPACT's MCID key criterion) and the PILE score after treatment was assessed.
  
  
  RESULTS
  A 30% or greater improvement on the self-report measures was significantly associated with improvement in physical function on the PILE task.
  
  
  CONCLUSIONS
  Despite extensive use of the MCID to evaluate effects of treatment in spinal disorders, this is the first empirical documentation of the validity of the IMMPACT's 30% change criterion compared with an objective physical anchor.
authors.affiliation: Department of Psychology, College of Science, The University of Texas at Arlington, Arlington, TX, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Gatchel
authors.forename: Tom G
authors.initials: TG
authors.lastname: Mayer
authors.forename: Yunhee
authors.initials: Y
authors.lastname: Choi
authors.forename: Roger
authors.initials: R
authors.lastname: Chou
mesh_terms: D000328:Adult; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000175:diagnosis* / Q000601:surgery; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D017060:Patient Satisfaction; D011446:Prospective Studies; D011788:Quality of Life; D013122:Spinal Diseases / Q000175:diagnosis* / Q000601:surgery; D011795:Surveys and Questionnaires; D016896:Treatment Outcome
keywords: Chronic disabling occupational lumbar spinal disorders; Functional restoration; IMMPACT; Minimal clinically important difference (MCID); PILE (progressive isoinertial lifting evaluation)