title: Test-retest reliability and validity of self-reported duration of computer use at work.
abstract: OBJECTIVE
  The aims of this study were to evaluate the test-retest reliability and the validity of self-reported duration of computer use at work.
  
  
  METHODS
  Test-retest reliability was studied among 81 employees of a research department of a university medical center. The employees filled out a web-based questionnaire twice with an in-between period of 14 days. Validity was studied among a group of 572 office workers who participated in an epidemiologic field study. A software program recorded the duration of computer use at work during the 3 months preceding the questionnaire.
  
  
  RESULTS
  The percentages of agreement for test-retest reliability were 75% [95% confidence interval (95% CI) 64-84] for total computer use and 67% (95% CI 55-77) for mouse use. The percentages of agreement between self-report and registration were 18% (95% CI 15-21) for total computer use and 16% (95% CI 13-19) for mouse use. Misclassification was mainly nondifferential in nature, since all of the evaluated subgroups showed at least 75% misclassification.
  
  
  CONCLUSIONS
  The use of self-reports lead to the misclassification of exposure to computer use for more than 80% of all persons. This misclassification is predominantly nondifferential in nature and can only partly be explained by limited test-retest reliability.
authors.affiliation: Body@Work TNO VUmc, EMGO Institute, Van der Boechorststraat 7, Amsterdam, Netherlands. stefan.ijmker@vumc.nl
authors.forename: Stefan
authors.initials: S
authors.lastname: IJmker
authors.forename: Josien N M
authors.initials: JN
authors.lastname: Leijssen
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: D000328:Adult; D003201:Computers; D012090:Cumulative Trauma Disorders / Q000517:prevention & control; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009140:Musculoskeletal Diseases / Q000517:prevention & control; D009426:Netherlands; D016273:Occupational Exposure / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D016526:Workload