The clinical utility of the GOLD classification of COPD disease severity in pulmonary rehabilitation.

The Global Initiative for Chronic Obstructive Lung Disease (GOLD) has introduced a four-stage classification of chronic obstructive pulmonary disease (COPD) severity. The present study investigated the discriminatory capacity of the GOLD classification for health status outcomes in patients with COPD. An additional analysis was performed to investigate the discriminatory capacity of a multidimensional staging system, i.e. the Body-Mass Index, Degree of Airflow Obstruction and Dyspnea, and Exercise Capacity Index (BODE index) for the outcome of quality of life. Retrospective analysis was performed on 253 COPD patients (30% stage II, 48% stage III, 22% stage IV), referred for outpatient pulmonary rehabilitation. Pulmonary function, exercise capacity, dyspnoea and quality of life were evaluated. Analyses of variance were used to detect differences between GOLD stages and BODE index quartiles, and scatterplots of individual responses were produced as well. The GOLD classification discriminated between stages for pulmonary function (p<0.001), exercise capacity (p<0.001), dyspnoea (p<0.001) and the activities section (p=0.001) of the St. George Respiratory Questionnaire (SGRQ). The BODE index discriminated between quartiles for the activities section (p<0.001), impacts section (p=0.04) and the total score (p=0.01) of the SGRQ. Scatterplots revealed marked inter-individual variation within each GOLD stage or BODE index quartile, and considerable overlap between stages for all health status outcomes. These findings show that the GOLD classification indeed can be used to discern groups of COPD patients, but due to large inter-individual variability it does not seem adequate as a basis for individual management plans in rehabilitation. The BODE index appeared to discriminate slightly better for quality of life, however, it still leaves a significant part of the variance unexplained.