© 2004 American Thoracic Society
The GOLD Classification Has Not Advanced Understanding of COPDDepartment of Pulmonary Medicine University Hospital Groningen Groningen, The Netherlands Defining and classifying the obstructive lung diseases has proven to be an extremely difficult task. The definition of asthma has been compared with explaining love: everybody knows what it is, but who would trust anybody else's definition (1)? Defining and grading the severity of COPD is not only attempting to define love, but also to classify how much in love one is. There are large cultural, temporal, gender, and above all personal differences. Since the Ciba symposium in 1958 (2), consensus reports with definitions and classifications from many national societies have appeared and have been updated several times. The distinctions between the different national reports, and between older and newer reports, are remarkable. In 1997, the U.S. National Heart Lung and Blood Institute and the World Health Organization convened an international workshop that reported, in 2001, the Global Initiative on Obstructive Lung Disease (3). The report has already been updated (4) and has created considerable awareness for COPD, an important goal (3). The report also incorporated a classification of severity of COPD. Several concerns regarding the GOLD classification can and should be made. The key points are that the classification is not evidence-based, does not advance our understanding of the pathophysiological mechanisms of COPD, has no relation to what matters to the patient, and is based on FEV1. As detailed below, I believe that these concerns are central to why the classification has not advanced our understanding of COPD to an important degree. The classification in the GOLD report is new and differs from most of the existing guidelines. This could mean that finally the light has been seen, the data are there, and we know how we can classify COPD in a manner that is both practicable and meaningful. If only this were the case. As in most guidelines, the classification is based on spirometry and especially on FEV1. None of our patients, however, complain about their FEV1 being low. We all know that FEV1 correlates poorly to all the things that do matter to patients: symptoms (5), quality of life (6), exacerbation frequency (7), and exercise intolerance (8). It is of significant importance that in the GOLD severity classification table, there is no mention of symptoms (except for grade 0). In other words, a diagnosis and severity grading of COPD would require no symptoms. FEV1 is by no means a good surrogate for symptoms, nor does it correlate very well with symptoms (9). An additional worry in using solely spirometry to classify COPD is that GOLD does little in the way of curbing the incorrect use of the term COPD, for instance in people under 40 (9) or even in children (10). The subdivision of COPD into emphysema and chronic bronchitis has in the GOLD report been removed from its definition, given the overlap between the two conditions and the poor delineation between them. A concise and legible section on pathogenesis and pathophysiology emphasizes the central importance of inflammation, and provides details of aspects of gas exchange derangements, hyperinflation, systemic effects, and mechanisms of dyspnea sensation. Both the understanding and the management of COPD would be greatly facilitated by a classification system that would take into account these different components of this complicated, heterogeneous disease. Such multidimensional staging systems are currently developed by several groups (11) and can hopefully be incorporated into one of the future updates of GOLD. If we are to inform policy makers on the global problem of COPD and its foreseeable demand on resources, we need to reach consensus on who does and who does not have COPD (12). In all guidelines hitherto, the cut-points of FEV1 are authority-, not evidence-, based, and GOLD is no exception. The reason that the severity grading is not based on validated cut-points of FEV1 is that the data are not available. But does it matter much which cut-points are used? I think it does: Celli and colleagues have compared the prevalence of COPD in 13,322 subjects as defined by five definitions. Rates in adults varied from 77 per 1,000 (self report) to 168 per 1,000 (fixed ratio FEV1/FVC < 0.70) (13). Viegi and coworkers have similarly shown that the rates in people above 45 years old varied enormously, from 12.2% with the definition of the European Respiratory Society to 57% with the criteria of the American Thoracic Society (9). In addition, the ratio of FEV1/FVC decreases with age. As a consequence, all criteria that incorporate a fixed ratio (not relative to the predicted value) will find an overdiagnosis of COPD in the elderly. This overdiagnosis has indeed been shown to occur with the GOLD criteria (14). There is another aspect in the GOLD classification that is completely novel: stage 0 (at risk). It is defined by chronic cough and sputum production, but with normal spirometry. Early identification of people with early disease can indeed have impact on future disease (15, 16). The concept that this stage 0 can reliably predict future COPD was recently tested in the Copenhagen City Heart Study (17). After a follow-up of 15 years, 20.5% of smokers with GOLD stage 0 had progressed to GOLD stage 1. In addition, however, 18.5% of smokers without any respiratory symptoms now fulfilled the criteria for stage 1. Moreover, stage 0 was not a stable feature because of variability of symptoms, which may explain the lack of predictive value. Not completely novel, yet not widely used is stage 1: an abnormal FEV1/FVC (< 0.70) but with an FEV1 above 80% predicted. Most clinicians will not traditionally score this as COPD, and future work will again need to unveil its value for predicting progression to the clinically more relevant stages 2–4. In the light of the global surge of COPD prevalence and morbidity, there is an urgent need to advance our understanding of COPD. In my opinion, the GOLD report makes a significant contribution and is an important step forward. Unfortunately, the classification of COPD in the current report is not. FOOTNOTES Conflict of Interest Statement: H.A.M.K. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. REFERENCES
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