THE CLINICAL UTILITY OF THE GOLD CLASSIFICATION OF COPD DISEASE SEVERITY IN PULMONARY REHABILITATION

Huijsmans RJ, de Haan A, ten Hacken NNHT, Straver RVM, van't Hula AJ

Respir Med. 2007; doi:10.1016/j.rmed.2007.07.008.

Summary

The Global Initiative for Chronic Obstructive Lung Disease (GOLD) has introduced a 4-stage classification of the 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, that is, 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, and 22% stage IV), referred for outpatient pulmonary rehabilitation. Pulmonary function, exercise capacity, dyspnea, 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 also produced. The GOLD classification discriminated between stages for pulmonary function (P < .001), exercise capacity (P < .001), dyspnea (P < .001), and the activities section (P < .001) of the St George's Respiratory Questionnaire (SGRQ). The BODE index discriminated between quartiles for the activities section (P < .001), impacts section (P < .04), and the total score (P < .01) of the SGRQ. Scatterplots revealed marked interindividual 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 because of large interindividual 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.

Editor's Comment. The GOLD staging of COPD is becoming accepted in clinical practice. The BODE index has been proposed to have greater discriminatory value, especially in exacerbation- and mortality-related outcomes, but has not yet seen much clinical penetration. This retrospective analysis demonstrates that the 2 methods do have justification for their use as they both allow discrimination, significantly but slightly differently, in several domains of the SGRQ. The real value of this report, however, is in its demonstration of the marked interindividual variability that prevents either of these staging methods from being useful discriminative indices in the individual patient and, therefore, suggesting that these are likely to be more useful as epidemiologic or population-/group-based tools.