Can GOLD Stage 0 provide information of prognostic value in chronic obstructive pulmonary disease?
In the recently published guidelines of the Global Initiative for Chronic Obstructive Lung Disease (GOLD) for chronic obstructive pulmonary disease (COPD), the staging system included a Stage 0 for subjects without airways obstruction but with respiratory symptoms, denoting these subjects "at risk" for COPD. Our aim was to validate this staging approach using data from three surveys in The Copenhagen City Heart Study, in which a sample of the general population was examined at baseline and in which, after 5 and 15 years, spirometry was performed at all surveys. Criteria for GOLD Stage 0 was fulfilled by 5.8% of the total adult population and 7.2% of smokers. After 5 and 15 years, 13.2 and 20.5%, respectively, of smokers with GOLD Stage 0 had developed COPD fulfilling criteria for GOLD Stage 1 or worse. This was the case for 11.6 and 18.5%, respectively, of smokers without respiratory symptoms. Further analyses using multivariate logistic regression analysis confirmed that GOLD Stage 0 was not identifying subsequent airways obstruction. When analyzing FEV(1) decline, Stage 0 carried a risk of excess decline. GOLD Stage 0 was not a stable feature, which may explain the lack of predictive value. In the Western world, smoking is still in itself the most important indicator of risk of COPD, and alternative markers of susceptibility in the population must be investigated.