Predictors of COPD exacerbations differ between grades of airflow limitation

History of exacerbations is a predictor of future exacerbations in COPD but there are also predictors that are independent of exacerbation history. However, it is unclear whether their relative contribution is consistent across different degrees of airflow limitation.

This analysis used data from COMPASS, a prospective study in COPD. Baseline demographics, clinical history, spirometry and patient-reported outcomes were collected. Multivariable models were created to predict moderate or severe exacerbations in the 18 months after baseline. Covariates included forced expiratory volume in 1 s (FEV₁) % predicted, Global Initiative for Chronic Obstructive Lung Disease (GOLD) grade, modified Medical Research Council (mMRC) and COPD Assessment Test (CAT) scores, and exacerbation history. Goodness of fit was tested using C-statistics.

At baseline there were 1696 patients; 89.6% males, 46.9% current smokers, mean±sd age of 65.4±7.5 years, post-bronchodilator FEV₁ 66.6±20.1% predicted and 0.5±1.0 moderate/severe exacerbations in the prior year. Over 18 months, 17.8% of patients had ≥1 moderate/severe exacerbation. The best fit model identified six independent variables, C-statistic 0.739. Subgroup analysis into GOLD grades I, II and III+IV combined showed different predictor patterns. In grade I, history of moderate exacerbations was the strongest predictor, together with chronic bronchitis and gastro-oesophageal reflux. In grades III+IV, only history of severe exacerbations and mMRC score were significant. Grade II showed an intermediate picture in which severe exacerbations, chronic bronchitis and gastro-oesophageal reflux were all significant.

There are multiple predictors of COPD exacerbations, which differ between GOLD grades. Future predictive models for exacerbation risk should take this into account.