title: Validation of a research case definition of Gulf War illness in the 1991 US military population.
abstract: BACKGROUND
  A case definition of Gulf War illness with 3 primary variants, previously developed by factor analysis of symptoms in a US Navy construction battalion and validated in clinic veterans, identified ill veterans with objective abnormalities of brain function. This study tests prestated hypotheses of its external validity.
  
  
  METHODS
  A stratified probability sample (n = 8,020), selected from a sampling frame of the 3.5 million Gulf War era US military veterans, completed a computer-assisted telephone interview survey. Application of the prior factor weights to the subjects' responses generated the case definition.
  
  
  RESULTS
  The structural equation model of the case definition fit both random halves of the population sample well (root mean-square error of approximation = 0.015). The overall case definition was 3.87 times (95% confidence interval, 2.61-5.74) more prevalent in the deployed than the deployable nondeployed veterans: 3.33 (1.10-10.10) for syndrome variant 1; 5.11 (2.43-10.75) for variant 2, and 4.25 (2.33-7.74) for variant 3. Functional status on SF-12 was greatly reduced (effect sizes, 1.0-2.0) in veterans meeting the overall and variant case definitions.
  
  
  CONCLUSIONS
  The factor case definition applies to the full Gulf War veteran population and has good characteristics for research.
authors: RTI International, Research Triangle Park, NC, USA.
authors: Vincent G
authors: VG
authors: Iannacchione
authors: Jill A
authors: JA
authors: Dever
authors: Carla M
authors: CM
authors: Bann
authors: Kathleen A
authors: KA
authors: Considine
authors: Darryl
authors: D
authors: Creel
authors: Christopher P
authors: CP
authors: Carson
authors: Heather
authors: H
authors: Best
authors: Robert W
authors: RW
authors: Haley
mesh_terms: D005260:Female; D047830:Gulf War; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D018923:Persian Gulf Syndrome / Q000175:diagnosis / Q000453:epidemiology*; D011159:Population Surveillance / Q000379:methods*; D011897:Random Allocation; D011795:Surveys and Questionnaires / Q000592:standards*; D014481:United States / Q000453:epidemiology; D014728:Veterans