© 2004 American Thoracic Society
The GOLD Classification Has Advanced Understanding of COPDDepartment of Medicine University Hospital Aintree Liverpool, England The Global Initiative for Chronic Obstructive Lung Disease (GOLD) was launched in 2001 following an NHLBI/WHO sponsored workshop which identified the need for a global response to the growing problem of COPD morbidity and mortality. The detailed set of recommendations for investigation and management were published and made available on the Web (www.goldcopd.com) as was an executive summary (1). GOLD built on the successful guidelines developed in the United States and Europe (2, 3), but included several new features that were thought to be important developments (4). Thus, the GOLD definition of COPD recognized its progressive nature, the role of pulmonary inflammation, and factors other than cigarette smoking and the genesis of the disease, a particularly important consideration in the developing world (5). The guidance on management was evidence-based, an approach followed in more recent guidelines where systematic review of the published literature drew much the same conclusion as advocated by the GOLD process (6). GOLD has developed a mechanism to review its recommendations as new data become available (7), and the changes are posted on the Web each summer. The July 2003 update included some important amendments to the original management scheme. Among these was a minor change in the GOLD classification of COPD severity. The classification of severity was based, in part, on the previous recommendations of both the American Thoracic and European Respiratory Societies using spirometry as a pragmatic surrogate for disease severity. In its current form, it identifies five stages of COPD, although stage 0, the presence of symptoms of cough, sputum, and breathlessness without airflow obstruction, was always conceived of as an opportunity for early identification of the disease rather than a necessary precursor of illness in all cases. Stages 1 to 4 are characterized by a reduced FEV1/FVC ratio less than 70% predicted and a reduced FEV1% predicted of greater than 80% for stage 1, 50–80% for stage 2, 30–50% for stage 3, and less than 30% for stage 4, although individuals with respiratory failure or cor pulmonale are assigned to this group irrespective of their FEV1. GOLD stresses that these cut-points have not been clinically validated and that patient contact is driven by symptoms, especially breathlessness and reduced exercise capacity, as well as by the development of complications. Indeed, management decisions are generally based on symptomatic response, e.g., to bronchodilator treatment, rather than changes in spirometry that are poorly predictive of symptomatic responsiveness (8). Nonetheless, spirometry is a necessary requirement for the diagnosis of COPD that should be available in all cases; it is sensible to use this information as a general pointer to future disease progression. One of the main aims of GOLD has been to promote research into COPD, and the classification adopted has played its part in doing this and providing a generally applicable yardstick against which other endpoints can be measured. These results have helped our understanding of COPD considerably. The choice of a fixed criterion of 0.7 for the FEV1/FVC ratio, irrespective of age, leads to a significantly greater number of people being diagnosed as having COPD compared with using the 70% of the age-predicted ratio (9). This finding has been confirmed in an analysis of the National Health and Nutrition Examination Survey (NHANES) data set, but the prevalence of COPD using the fixed ratio of 0.7 in patients with GOLD stage 2 and below was very similar to that based on the % predicted value of the ratio (10). GOLD specifies the use of the postbronchodilator FEV1 as the most robust way of diagnosing COPD, and this is important in epidemiologic studies. Application of the GOLD classification to the large European Community Respiratory Health Study has shown that 1% of individuals between the ages of 20 and 44 years appear to suffer from COPD and also that individuals with GOLD stage 0 in this age group are as symptomatic as those with more severe illness (11). GOLD stage 0 does not describe the natural history of all COPD patients, as was demonstrated in a retrospective review of a large population study conducted in Copenhagen, where cough and sputum production were no more likely to predict the future progression of FEV1 than was their absence (12). Interpreting such data is difficult, especially given changes in smoking habits and possible day-to-day variations in symptoms. Future prospective studies, such as the follow-up of the European Community Respiratory Health Study, should cast further light on this point. The choice of a 50% FEV1 threshold to separate stages 2 and 3 was originally based on the observation of differing frequencies of exacerbations of disease in those with more severe illness (13) and the more evident benefits of combining different inhaled treatments in these sicker patients (14, 15). The more frequent exacerbations may explain why studies examining the relationship of GOLD classification to health status find a clear disjunction between stages 2 and 3 (16). The original GOLD severity classification has been shown to have some limitations. It does not necessarily relate to individual symptom severity, hence the emphasis on symptom assessment and the clinical evaluation; nor does it address the role of other measures that may be relevant to disease progression, e.g., the presence of emphysema on CT scanning or of inflammatory markers indicating pulmonary inflammation. It does, however, provide a useful measurement that contributes to the patient's overall evaluation, and the criteria directed by GOLD have now been adopted by both national and international guidelines as reasonable points for stratifying disease severity (17). In time, newer approaches to disease assessment may supersede this FEV1–based system, (18) but, at present, it has the advantage of relative simplicity and potential universal application. At least as important, by setting a standard, GOLD has stimulated researchers to challenge its assumptions and use this classification as an aid in the interpretation of other patient-related observations. In this GOLD has succeeded more than its originators dared hope. FOOTNOTES Conflict of Interest Statement: P.M.A.C. has received research funding of $500,000 from GlaxoSmithKline to support work on the genetics of chronic obstructive pulmonary disease and has participated in advisory boards for GlaxoSmithKline, AstraZeneca, Boehringer Ingelheim and Pfizer which have not exceeded the payment threshold for declaration. REFERENCES
This article has been cited by other articles:
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
