It is accepted that a single measurement of FEV1 incompletely represents the complex clinical consequences of COPD because: 1) many patients are practically asymptomatic; 2) persistant cough and sputum production often precede the development of airflow limitation [3] and, in others, the first symptom may be the development of dyspnoea with previously tolerated activities; and 3) in the clinical course of the disease, systemic consequences, such as weight loss [10, 11], and peripheral muscle wasting and dysfunction [12, 13], may develop.

Due to these and other factors, a staging system that could offer a composite picture of disease severity is highly desirable, although it is currently unavailable. However, spirometric classification is useful in predicting outcomes such as health status and mortality, and should be evaluated. In addition to the FEV1, the BMI [10, 11] and dyspnoea [14] have proved useful in predicting outcomes such as survival and this document recommends that they be evaluated in all patients.

BMI is easily obtained by dividing the weight (in kg) over the height (in m²). Values <21 kg•m^-2 are associated with increased mortality.

Functional dyspnoea can be assessed by the Medical Research Council dyspnoea scale.

0: not troubled with breathlessness except with strenuous exercise.
1: troubled by shortness of breath when hurrying or walking up a slight hill.
2: walks slower than people of the same age due to breathlessness or has to stop for breath when walking at own pace on the level.
3: stops for breath after walking ~100 m or after a few minutes on the level.
4: too breathless to leave the house or breathless when dressing or undressing.