Abstract
Redesign current grading of obstructive lung disease so that it is clinically relevant and free of biases related to age, height, sex and ethnic group.
Spirometric records from 17,880 subjects (50.4% females) from hospitals in Australia and Poland, and 21,191 records (53.0% females) from 2 epidemiological studies (age 18–95 years).
We adopted the American Thoracic Society and European Respiratory Society (ATS/ERS) criteria for airways obstruction based on an FEV1/(F)VC ratio below the 5th percentile and graded the severity of pulmonary function impairment using z-scores for FEV1 which signify how many standard deviations a result is from the mean predicted value.
Using the lower limit of normal for FEV1/(F)VC and z-scores for FEV1 of −2, −2.5, −3 and −4 to delineate severity grades of airflow limitation leads to close agreement with ATS/ERS severity classifications and removes age, sex and height related bias.
The new classification system is simple, easily memorised and clinically valid. It retains previously established associations with clinical outcomes and avoids biases due to the use of percent predicted FEV1. Combined with the Global Lung Function prediction equations it provides a world-wide diagnostic standard free of bias due to age, height, sex and ethnic group.
- ERS