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Impact of using different predictive equations on the prevalence of chronic byssinosis in textile workers in Pakistan
  1. Asaad Ahmed Nafees1,2,
  2. Muhammad Zia Muneer1,
  3. Sara De Matteis2,3,
  4. Andre Amaral2,
  5. Peter Burney2,
  6. Paul Cullinan2
  1. 1 Department of Community Health Sciences, Aga Khan University, Karachi, Pakistan
  2. 2 National Heart and Lung Institute, Imperial College London, London, UK
  3. 3 Department of Medical Sceinces and Public Health, University of Cagliari, Cagliari, Italy
  1. Correspondence to Dr Asaad Ahmed Nafees, Department of Community Health Sciences, The Aga Khan University, Karachi, Pakistan; asaad.nafees{at}


Objective Byssinosis remains a significant problem among textile workers in low/middle-income countries. Here we share our experience of using different prediction equations for assessing ‘chronic’ byssinosis according to the standard WHO classification using measurements of forced expiratory volume in 1 s (FEV1).

Methods We enrolled 1910 workers in a randomised controlled trial of an intervention to improve the health of textile workers in Pakistan. We included in analyses the 1724 (90%) men who performed pre-bronchodilator spirometry tests of acceptable quality. We compared four different equations for deriving lung function percentage predicted values among those with symptoms-based byssinosis: the third US National Health and Nutrition Examination Survey (NHANES-III, with ‘North Indian and Pakistani’ conversion factor); the Global Lung Function Initiative (GLI, ‘other or mixed ethnicities’); a recent equation derived from survey of a western Indian population; and one based on an older and smaller survey of Karachi residents.

Results 58 men (3.4%) had symptoms-based byssinosis according to WHO criteria. Of these, the proportions with a reduced FEV1 (<80% predicted) identified using NHANES and GLI; Indian and Pakistani reference equations were 40%, 41%, 14% and 12%, respectively. Much of this variation was eliminated when we substituted FEV1/forced vital capacity (FVC) ratio (<lower limit of normality) as a measure of airway obstruction.

Conclusion Accurate measures of occupational disease frequency and distribution require approaches that are both standardised and meaningful. We should reconsider the WHO definition of ‘chronic’ byssinosis based on changes in FEV1, and instead use the FEV1/FVC.

  • occupational health
  • respiratory system
  • air pollution
  • indoor

Data availability statement

Data are available upon reasonable request.

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Data availability statement

Data are available upon reasonable request.

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  • Contributors AAN led this work in conceptualisation, analysis and write-up. MZM supported its statistical analysis. SDM, PB, AA and PC provided supervision throughout this work. All authors read and approved the manuscript before submission.

  • Funding This study was suppoted by Wellcome Trust (Ref: 206757/Z/17/Z).

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.