title: Estimates of restrictive ventilatory defect in the mining industry. Considerations for epidemiological investigations: a cross-sectional study.
abstract: OBJECTIVE
  (1) To assess the impact of American Thoracic Society and European Respiratory Society (ATS/ERS) 'acceptability' and 'usability' criteria for spirometry on the estimates of restrictive ventilatory defect in a population of taconite miners. (2) To compare estimates of restrictive ventilatory defect with three different pulmonary function tests (spirometry, alveolar volume (VA) and diffusing capacity (DL,CO)). (3) To assess the role of population characteristics on these estimates.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  Current and former workers in six current taconite mining operations of northeastern Minnesota were surveyed.
  
  
  METHODS
  We attempted to enrol 3313 participants. Of these, 1353 responded while 1188 current and former workers fully participated in the survey and 1084 performed complete pulmonary function testing and were assessed.
  
  
  METHODS
  We applied ATS/ERS acceptability criteria for all tests and categorised participants into groups according to whether they fully met, partially met or did not meet acceptability criteria for spirometry. Obstruction and restriction were defined utilising the lower limit of normal for all tests. When using VA, restriction was identified after excluding obstruction.
  
  
  RESULTS
  Only 519 (47.9%) tests fully met ATS/ERS spirometry acceptability criteria. Within this group, 5% had obstruction and 6%, restriction on spirometry. In contrast, among all participants (N=1084), 16.8% had obstruction, while 4.5% had restriction. VA showed similar results in all groups after obstruction was excluded. Impaired gas transfer (reduced DL,CO) was identified in less than 50% of restriction identified by either spirometry or VA. Body mass index (BMI) was significantly related to spirometric restriction in all groups.
  
  
  CONCLUSIONS
  Population estimates of restriction using spirometry or VA varied by spirometric acceptability criteria. Other factors identified as important considerations in the estimation of restrictive ventilatory defect included increased BMI and gas transfer impairment in a relatively smaller proportion of those with spirometric restriction. These insights are important when interpreting population-based physiological data in occupational settings.
authors.affiliation: Division of Environmental Health Sciences, University of Minnesota School of Public Health, Minneapolis, Minnesota, USA.
authors.forename: Nnaemeka U
authors.initials: NU
authors.lastname: Odo
authors.forename: Jeffrey H
authors.initials: JH
authors.lastname: Mandel
authors.forename: David M
authors.initials: DM
authors.lastname: Perlman
authors.forename: Bruce H
authors.initials: BH
authors.lastname: Alexander
authors.forename: Paul D
authors.initials: PD
authors.lastname: Scanlon
keywords: Epidemiology; Occupational & Industrial Medicine; Public Health; Respiratory Medicine (see Thoracic Medicine); Statistics & Research Methods