Temporal transitions in COPD severity stages within the GOLD 2017 classification system
The diagnosis and staging of chronic obstructive pulmonary disease (COPD) is controversial. At the end of 2016, the Global Initiative for Chronic Obstructive Lung Disease (GOLD) modified its global COPD severity staging recommendations, to be based on symptoms and history of exacerbations exclusively, and not including forced expiratory volume in one second (FEV1). However, the stability of the new staging is unknown, as is the frequency of the individual transitions in COPD severity beyond one year.
The objective of this study was to determine the longer-term distribution (longer than one year and up to five years) of the GOLD COPD stage transitions.
Soriano and colleagues analysed data from the CHAIN study, a multicentre, observational, prospective cohort of COPD patients. They investigated 959 COPD patients with a mean age of 66.3 years, of whom 19% were female and 33.3% were smokers. At baseline, their severity was distributed (according to GOLD criteria) as 37.7% A, 38.3% B, 8.2% C and 15.7% D. Participants were followed up over the five-year study period, with clinic visits every 12 months and telephone interviews every six. The recruitment period ran from January 2010 to March 2012. A Markov chain model was created and analysed, in which the probability of an event is dependent solely on the state attained in the previous event.
Although its novelty, size and length of follow-up represented study strengths, the investigators noted its limitations. As an observational, non-interventional study, there were determinants that may have had a role in the observed stage transitions, for example, smoking cessation and adherence/variations in COPD pharmacotherapy. Also, over the course of five years the cohort size had shrunk to 388 patients (38.2% of baseline).
The authors observed that, although the proportions of all stages remained largely stable in the overall population after baseline assessment (from A being the most frequent, to B, D and then C as the least frequent), there were significant changes between stages at the individual patient level, especially for the more severe stages, up to five years of follow-up.
The CHAIN study was funded by AstraZeneca Spain S.A.