title: Comparing current definitions of return to work: a measurement approach.
abstract: BACKGROUND
  Return-to-work (RTW) status is an often used outcome in work and health research. In low back pain, work is regarded as a normal activity a worker should return to in order to fully recover. Comparing outcomes across studies and even jurisdictions using different definitions of RTW can be challenging for readers in general and when performing a systematic review in particular. In this study, the measurement properties of previously defined RTW outcomes were examined with data from two studies from two countries.
  
  
  METHODS
  Data on RTW in low back pain (LBP) from the Canadian Early Claimant Cohort (ECC); a workers' compensation based study, and the Dutch Amsterdam Sherbrooke Evaluation (ASE) study were analyzed. Correlations between outcomes, differences in predictive validity when using different outcomes and construct validity when comparing outcomes to a functional status outcome were analyzed.
  
  
  RESULTS
  In the ECC all definitions were highly correlated and performed similarly in predictive validity. When compared to functional status, RTW definitions in the ECC study performed fair to good on all time points. In the ASE study all definitions were highly correlated and performed similarly in predictive validity. The RTW definitions, however, failed to compare or compared poorly with functional status. Only one definition compared fairly on one time point.
  
  
  CONCLUSIONS
  Differently defined outcomes are highly correlated, give similar results in prediction, but seem to differ in construct validity when compared to functional status depending on societal context or possibly birth cohort. Comparison of studies using different RTW definitions appears valid as long as RTW status is not considered as a measure of functional status.
authors.affiliation: Institute for Work and Health, 481 University Avenue, Suite 800, Toronto, ON, M5G 2E9, Canada. isteenstra@iwh.on.ca
authors.forename: I A
authors.initials: IA
authors.lastname: Steenstra
authors.forename: H
authors.initials: H
authors.lastname: Lee
authors.forename: E M M
authors.initials: EM
authors.lastname: de Vroome
authors.forename: J W
authors.initials: JW
authors.lastname: Busse
authors.forename: S J
authors.initials: SJ
authors.lastname: Hogg-Johnson
mesh_terms: D000293:Adolescent; D000328:Adult; D002170:Canada; D004185:Disability Evaluation; D004651:Employment; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D017116:Low Back Pain / Q000534:rehabilitation*; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D009784:Occupational Diseases / Q000534:rehabilitation*; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D011594:Psychometrics; D015203:Reproducibility of Results; D018582:Sick Leave; D011795:Surveys and Questionnaires; D014937:Work; D014942:Workers' Compensation; D055815:Young Adult