**10. Stage of disease severity and progression**

The GOLD staging system is based on the FEV1/FVC ratio(see Table 2). It has been criticized for underestimating the importance of the extrapulmonary manifestations of COPD in predicting outcome(GOLD,2006;Bourdin et al,2009). The BODE index addresses this criticism. The four factors included in the BODE index are weight (BMI), airway obstruction (FEV1), dyspnea (Medical Research Council dyspnea score), and exercise capacity (sixminute walk distance)(see Table 3). This index provides better prognostic information than the FEV1 alone to assess an individual's risk of death or hospitalization due to COPD. However, it is not used to guide therapy.

A component of disease assessment that is used in research studies is to evaluate the impact of airflow limitation on quality of life. The St. George's Respiratory Questionnaire (SGRQ) is a 76 item questionnaire that includes three component scores (ie, symptoms, activity, and impact on daily life) and a total score(Jones et al.,1991). It has been validated in patients with COPD, asthma, and bronchiectasis. Another questionnaire based instrument to assess quality of life is the Chronic Respiratory Disease Questionnaire (CRDQ) (Guyatt et al.,1987).


BMI, body mass index; FEV1, forced expiratory volume in 1 second.

Table 3. BODE Index for Staging COPD (Celli et al.,2004)
