Clinically important deterioration in a mild-moderate COPD population

Clinically important deterioration (CID), a composite of exacerbation, declines in lung function and health status has been studied as an indicator of disease worsening in moderate-severe COPD clinical populations. We assessed whether CID is predictive of worsening over 18 months in a population-based mild-moderate COPD cohort.

Canadian Cohort Obstructive Lung disease (CanCOLD) participants with COPD were assessed over 18 months for CID, and over the next 18 months for outcomes. Their association was then examined: 1) defined into threshold-based binary variables, the declines in forced expiratory volume in 1 s (FEV₁), health status and dyspnoea, using logistic regression models; 2) time to moderate/severe exacerbation and rates of moderate/severe exacerbations using Cox proportional hazards and Poisson regression, respectively.

Out of 420 participants, 252 (60%) demonstrated CID (definition 1, St George's Respiratory Questionnaire (SGRQ)). Presence of CID at 18 months showed association with future moderate/severe exacerbation (not statistically significant), worsening health status (COPD Assessment Test (CAT) score), and dyspnoea. As a component, FEV₁ was found to be less informative, compared with exacerbation for health status outcome (OR 4.31, 95% CI 1.29-14.41 for ≥8-unit increase in SGRQ) alongside future exacerbation, and SGRQ health status component, for future health status decline (OR 0.33, 95% CI 0.17-0.66 for ≥4-unit increase in SGRQ and OR 0.53, 95% CI 0.30-0.94 for ≥2-unit increase CAT score).

Our finding of informative CID components seems to support recommendations of emphasis on exacerbation history and health status, over severity of airway obstruction in clinical assessments to predict outcomes. Suitable adaptations of the current CID definition may be needed for mild-moderate COPD populations.