Classifying the severity of COPD: are the new severity scales better than the old?

BACKGROUND: Forced expiratory volume in 1 second cut-off points establish the severity of chronic obstructive pulmonary disease (COPD).

OBJECTIVES: To compare how the American Thoracic Society (ATS), the British Thoracic Society (BTS), the Global Initiative for COPD (GOLD) and the ATS-European Respiratory Society (ATS-ERS) guidelines for rating COPD severity predict several significant outcomes.

DESIGN: Five-year prospective cohort study. Spirometry was performed and health-related quality of life (HRQoL) assessed using the Short Form 36 Health Survey and the Saint George's Respiratory Questionnaire. Hospital admissions resulting from COPD exacerbation and mortality during a 5-year follow-up period were recorded.

RESULTS: In all guidelines, the number of admissions was directly associated with COPD severity. The sensitivity and specificity for 5-year respiratory mortality were respectively 0.21 and 0.97 for the GOLD/ATS-ERS, 0.51 and 0.79 for the BTS, and 0.37 and 0.89 for the ATS guidelines. A similar pattern was seen for all-cause mortality. For HRQoL, statistically significant differences between guidelines were seen only for the BTS and ATS scales.

CONCLUSIONS: These guidelines did not consistently stratify patients with regard to 5-year mortality and HRQoL. Although the BTS system was slightly superior, none of the guidelines were closely related to these outcomes. Other instruments are needed for a better determination of the severity of COPD.