Comparing the 2007 and 2011 GOLD Classifications as Predictors of all-Cause Mortality and Morbidity in COPD

To better classify patients with chronic obstructive pulmonary disease (COPD) for prognostic purposes and to tailor treatment, the Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2007 classification was revised in 2011. The primary aim of the current data analyses was to evaluate the accuracy of the GOLD 2007 and 2011 GOLD classifications to predict all-cause mortality and morbidity in a well-described COPD cohort. The prognostic values of both GOLD classifications, expressed as the C-statistic, were assessed in the Cohort of Mortality and Inflammation in COPD (COMIC) study of 795 COPD patients, with a follow-up of 3 years. Outcomes were all-cause mortality and morbidity. Morbidity was defined as time until first COPD-related hospitalisation and time until first community-acquired pneumonia (CAP). The prognostic value of the GOLD 2011 classification was compared between symptom classification based on the modified Medical Research Council (mMRC) score and the Clinical COPD Questionnaire (CCQ) scores with two different thresholds. Although the GOLD 2011 CCQ classification had the highest accuracy to predict mortality and morbidity in our study, the C-statistics differed only numerically. Furthermore, our study showed that the instrument used to determine the level of symptoms in the GOLD 2011 classification has not only important consequences on the mortality prognosis, but also affects the morbidity prognosis in COPD. Therefore, patients' estimated prognosis could alter when different types of tools are used to evaluate the prognosis.