Effects of spirometry standards in two occupational cohorts

Area of Science:

• Occupational Medicine
• Epidemiology
• Pulmonary Function Testing

Background:

• Current spirometry guidelines exclude subjects with nonreproducible lung function tests (test failures) from epidemiological analyses.
• The characteristics and potential impact of excluding these subjects on occupational respiratory disease research are not well understood.

Purpose of the Study:

• To describe the characteristics of subjects with test failures in two occupational respiratory disease cohorts.
• To investigate the potential selection bias introduced by excluding subjects with test failures from epidemiological analyses.

Main Methods:

• Analysis of two cohorts: 415 Chinese cotton textile workers and 378 asbestos-exposed machinists.
• Comparison of disease prevalence and lung function (FEV1) between subjects with reproducible and nonreproducible spirometry tests.
• Regression analysis to assess the association between occupational exposures and FEV1, with and without subjects with test failures.

Main Results:

• In cotton textile workers, byssinosis prevalence was higher in subjects with test failures (13.3%) than those with repeatable tests (5.8%).
• In asbestos-exposed machinists, chronic bronchitis was significantly more prevalent among subjects with test failures.
• Excluding subjects with test failures altered the estimated association between cotton dust exposure and FEV1.
• Subjects with test failures appeared to have lower unobserved FEV1 values on average.

Conclusions:

• Exclusion of subjects with nonreproducible lung function tests may lead to selection bias in occupational respiratory disease studies.
• This exclusion may underestimate the true prevalence of respiratory diseases and the effects of occupational exposures.
• Revisiting current spirometry exclusion criteria may be warranted to ensure more accurate epidemiological findings.