title: Test-retest reliability and concurrent validity of a web-based questionnaire measuring workstation and individual correlates of work postures during computer work.
abstract: BACKGROUND
  "Ergonomic" questionnaires are widely used in epidemiological field studies to study the association between workstation characteristics, work posture and musculoskeletal disorders among office workers. Findings have been inconsistent regarding the putative adverse effect of work postures. Underestimation of the true association might be present in studies due to misclassification of subjects to risk (i.e. exposed to non-neutral working postures) and no-risk categories (i.e. not exposed to non-neutral working postures) based on questionnaire responses. The objective of this study was to estimate the amount of misclassification resulting from the use of questionnaires.
  
  
  METHODS
  Test-retest reliability and concurrent validity of a newly developed questionnaire was assessed. This questionnaire collects data on workstation characteristics and on individual characteristics during computer work (i.e. work postures, movements and habits). Pictures were added where possible to provide visual guidance. The study population consisted of 84 office workers of a research department. They filled out the questionnaire on the Internet twice, with an in-between period of 2 weeks. For a subgroup of workers (n=38), additional on-site observations and multiple manual goniometer measurements were performed.
  
  
  RESULTS
  Percentage agreement ranged between 71% and 100% for the test-retest analysis, between 31% and 100% for the comparison between questionnaire and on-site observation, and between 26% and 71% for the comparison between questionnaire and manual goniometer measurements. For 9 out of 12 tested items, the percentage agreement between questionnaire and manual goniometer measurements was below 50%.
  
  
  CONCLUSIONS
  The questionnaire collects reliable data on workstation characteristics and some individual characteristics during computer work (i.e. work movements and habits), but does not seem to be useful to collect data on work postures during computer work in epidemiological field studies among office workers.
authors.affiliation: Body@Work TNO VUmc, Research Centre Physical Activity, Work and Health, The Netherlands.
authors.forename: Stefan
authors.initials: S
authors.lastname: IJmker
authors.forename: Janneke
authors.initials: J
authors.lastname: Mikkers
authors.forename: Birgitte M
authors.initials: BM
authors.lastname: Blatter
authors.forename: Allard J
authors.initials: AJ
authors.lastname: van der Beek
authors.forename: Willem
authors.initials: W
authors.lastname: van Mechelen
authors.forename: Paulien M
authors.initials: PM
authors.lastname: Bongers
mesh_terms: D003201:Computers; D004867:Equipment Design; D006804:Ergonomics; D006801:Humans; D007374:Interior Design and Furnishings; D020407:Internet; D009140:Musculoskeletal Diseases / Q000517:prevention & control; D016272:Occupational Health; D011187:Posture / Q000502:physiology*; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D017132:Workplace