title: Block design allowed for control of the Hawthorne effect in a randomized controlled trial of test ordering.
abstract: OBJECTIVE
  To evaluate the value of balanced incomplete block designs in quality improvement research, and their capacity to control for the Hawthorne effect.
  
  
  METHODS
  General practitioners teams were randomized into three arms and received an intervention on test ordering, relating to tests for two groups of clinical problems (A tests and B tests). In the two trials within the block design, we tried to control for the Hawthorne effect by comparing the complete intervention in both arms on either the A (arm I) or B tests (arm II); the arms acted as blind controls for each other. In the classical trial, the complete intervention on B tests (arm II) was compared with a control arm without any intervention on B tests (arm III).
  
  
  RESULTS
  The trials with the block design yielded statistically significant changes in the numbers of A tests ordered (P=.013), but not in the numbers of B tests ordered (P=.29). In the classical design, the complete intervention reached a marginally significant change in the B tests (P=.068). The Hawthorne effect was the same for both arms of the block design. In the classical design, the effect could to some extent be attributed to the Hawthorne effect.
  
  
  CONCLUSIONS
  Our block design allowed us to control for the Hawthorne effect. Suitable use of block designs may further our knowledge of nonspecific effects in quality improvement research.
authors.affiliation: Centre for Quality of Care Research (WOK), Care and Public Health Research Institute, Department of General Practice, Maastricht University, PO.Box 616, NL-6200 MD Maastricht, The Netherlands. wim.verstappen@hag.unimass.nl
authors.forename: Wim H J M
authors.initials: WH
authors.lastname: Verstappen
authors.forename: Trudy
authors.initials: T
authors.lastname: van der Weijden
authors.forename: Gerben
authors.initials: G
authors.lastname: ter Riet
authors.forename: Jeremy
authors.initials: J
authors.lastname: Grimshaw
authors.forename: Ron
authors.initials: R
authors.lastname: Winkens
authors.forename: Richard P T M
authors.initials: RP
authors.lastname: Grol
mesh_terms: D003955:Diagnostic Tests, Routine / Q000706:statistics & numerical data*; D004311:Double-Blind Method; D015987:Effect Modifier, Epidemiologic; D006801:Humans; D010821:Physicians, Family