• Asthma
• asthma mechanisms
• asthma pharmacology
• COPD mechanisms
• COPD pharmacology
• emphysema
• exercise
• lung physiology

The current international guidelines for the diagnosis and management of COPD recognise spirometry as a major criterion to confirm a clinical diagnosis of COPD.1–3 The specific role of spirometry for the diagnosis of COPD is to identify the presence if airflow obstruction, which is the essential requirement for the definition of the disease. Although a reduction of the ratio of forced expiratory volume in one second (FEV₁) to forced vital capacity (FVC) has been consistently adopted as an unquestionable sign of airflow obstruction, no consensus has been achieved regarding the cut-off to separate healthy from obstructed subjects.

In 1986 the American Thoracic Society (ATS) suggested an obstructive abnormality be present when FEV₁/FVC is <0.75 independent of age and sex.4 By contrast, the European Respiratory Society (ERS) recommended the use of the ratio of FEV₁ to slow vital capacity (VC) with cut-off values as percentage of predicted for age and sex (88% for males and 89% for females).5 These values, which roughly correspond to the lower 5th percentiles of a healthy population, take into account the physiological age-related decrease of lung elastic recoil. In line with this statistics-based approach, the recent joint document ATS/ERS on standardisation if lung function testing6 indicated an FEV₁/VC or FEV₁/FVC below the lower 5th percentile as the lower limit of normality (LLN) to define airflow obstruction. At variance with this recommendation, the Global Initiative for Chronic Obstructive Lung Disease …