Temporal transitions in COPD severity stages within the GOLD 2017 classification system

Background: The stability of the new GOLD 2017 COPD staging is unknown, as well as the frequency of individual transitions in COPD stages beyond one year. Methods: All COPD participants in the CHAIN cohort were re-analysed according to GOLD 2017 up to five years of follow-up. Their individual changes within COPD stages were aggregated into cohort-wide Markov chains; group stability was evaluated using joinpoint regression. Results: At baseline, 959 COPD patients were distributed according to GOLD 2017 stages as 37.7% in A, 38.3% B, 8.2% C, and 15.7% D. The group proportion of patients in each stage was maintained from years one to five. However, we found significant changes between stages at the individual patient level, especially in the more severe stages. The probability of a patient remaining in the same GOLD 2017 COPD stage for two consecutive years ranged during the five years of follow-up for stage C from 16% to 31% per year, while for D from 23% to 43% per year, indicating substantial variation either increasing or decreasing severity for the vast majority of patients. Conclusions: We conclude that group stability observed in COPD staging according to GOLD 2017 recommendations is paired with a large variability at the individual patient level.