Effects of changing reference values on the interpretation of spirometry for rubber workers

Area of Science:

• Occupational Health
• Pulmonary Medicine
• Industrial Hygiene

Background:

• Rubber workers face increased respiratory risks from industrial exposure.
• The National Health and Nutrition Assessment Survey (NHANES) is increasingly used for interpreting spirometry in occupational settings.
• Changes in spirometric prediction equations can significantly affect monitoring programs for these workers.

Purpose of the Study:

• To compare the diagnostic differences between the Knudson and NHANES III spirometric prediction equations.
• To evaluate these differences in nonsmoking workers within the rubber industry.

Main Methods:

• A cross-sectional study involving 75 nonsmoking rubber industry workers with at least two years of occupational exposure.
• Spirometry was performed following established American Thoracic Society/European Respiratory Society guidelines.
• Workers had access to engineered controls and respiratory protection.

Main Results:

• The NHANES III equation identified 4% of workers as having restrictive disease (based on FVC) who were classified as normal by the Knudson equation.
• The Knudson equation identified 8% more workers with small airway obstruction (FEF 25-75 <50%) compared to the NHANES III equation.

Conclusions:

• The NHANES III equation demonstrates superior sensitivity in detecting restrictive lung diseases among rubber workers compared to the Knudson equation.
• The Knudson equation exhibits greater sensitivity in identifying obstructive lung patterns.
• These findings highlight the importance of equation selection for accurate spirometry interpretation in occupational respiratory health surveillance.