ERS/ATS spirometry interpretation standards: a gap in grading severity of airflow obstruction

The European Respiratory Society/American Thoracic Society (ERS/ATS) technical standard on interpretive strategies for routine lung function tests made several major changes in how to interpret spirometry [1]. For the classification of severity, the recommendation is to use z-scores based on age, height and sex. The recommended three-level system would deem a z-score >−1.645 as normal, z-scores between −1.65 and −2.5 as mild impairment, z-scores between −2.5 and −4 as moderate impairment, and z-scores <−4 as severe impairment. There is a gap in the classification scheme recommended by ERS/ATS for staging severity of airflow obstruction