Do GOLD stages of COPD severity really correspond to differences in health status?

The purpose of this study was to assess whether different stages of chronic obstructive pulmonary disease (COPD) severity defined according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria correlate with meaningful differences in health status. A total of 381 COPD patients, aged 73 +/- 6 yrs, were classified in the five GOLD stages. Disease-specific (St George Respiratory Questionnaire (SGRQ)) and generic indexes of health status were measured in all patients. Multivariate analysis of covariance or Kruskal Wallis tests were used to compare health status indexes across the spectrum of GOLD stages of COPD severity. GOLD stages of COPD severity significantly differed in SGRQ components and Barthel's index, but not in the indexes assessing cognitive and affective status and quality of sleep. The largest variation in health status was observed at the transition from stage IIa to stage IIb, while there were no other significant differences between consecutive stages. Both female sex and comorbidity were associated with a greater impact of COPD on the health status. In conclusion, the upper limit of stage IIb (forced expiratory volume in one second of 49%) marks a threshold for dramatic worsening of health status. Progression of chronic obstructive pulmonary disease severity from stage 0 to stage IIa does not correspond to any meaningful difference in health status.