title: Respiratory symptom reporting error in occupational surveillance of older farmers.
abstract: OBJECTIVE
  Agricultural health studies often use respiratory symptom report as a surrogate measure of disease and exposure; little data exists on the accuracy of symptom report in a work-motivated population.
  
  
  METHODS
  Screening spirometry and telephone survey data for Kentucky male farmers >55 year (n = 134) in the NIOSH Farm Family Health and Hazard Surveillance Project were compared to investigate the accuracy of symptom report as a measure of respiratory disease risk in older farmers.
  
  
  RESULTS
  The prevalence of reported obstructive respiratory symptoms was 0.24 (95% CI = 0.17 to 0.31); objective measures increased prevalence to 0.35 (95% CI = 0.27 to 0.43). Customary symptom questions did not reliably reflect objective indicators of respiratory impairment.
  
  
  CONCLUSIONS
  Older farmers may not accurately report respiratory symptoms. Whether by intention or misinterpretation of physical cues, self-reporting errors in this population may introduce misclassification bias.
authors.affiliation: College of Medicine, University of Kentucky, Lexington, KY 40536, USA. nejohn2@uky.edu
authors.forename: Nancy E
authors.initials: NE
authors.lastname: Johnson
authors.forename: Steven R
authors.initials: SR
authors.lastname: Browning
authors.forename: Susan M
authors.initials: SM
authors.lastname: Westneat
authors.forename: T Scott
authors.initials: TS
authors.lastname: Prince
authors.forename: Mark B
authors.initials: MB
authors.lastname: Dignan