Definitions of early COPD and predictors for disease progression: a systematic review

Early chronic obstructive pulmonary disease (COPD) is considered to represent the initial phase of the disease. However, inconsistent terminology and lack of standardised definitions hinders research and clinical application. This systematic review examined clinical research on early COPD, analysed terms and definitions used, and evaluated predictors of disease progression. This serves as a platform to reach consensus and direct future research to target early disease states and improve patient outcomes.

Utilising a standardised protocol, we systematically screened all clinical studies on early COPD. Titles and abstracts were reviewed and compared against inclusion and exclusion criteria. Stage 1 assessed terminology and definitions and stage 2 evaluated predictors of progression. Two independent people reviewed studies at each stage. Study quality was appraised using a modified Downs and Black checklist.

We identified 4871 articles, 1759 were screened after duplicate removal. The terms used included PRISm (preserved ratio impaired spirometry) (104 articles), GOLD 0 (Global Initiative for Chronic Obstructive Lung Disease stage 0) (63), early COPD (37), at-risk COPD (35) and pre-COPD (30). Definitions were heterogeneous and proposed early COPD definitions were not routinely used. Stage 2 included 43 full-text articles from cohort studies, of which 93% were of good quality. Predictors of progression included age (n=13 articles), smoking history (12), symptoms (12), exacerbations (one), lung function measures (20), computed tomography metrics (14), risk tools (three) and machine learning approaches (three).

We demonstrate an urgent need for consensus on clinically applicable definitions of the early disease course of COPD, prior to diagnosis. We highlight predictors of progression; these need validation to enable stratification of individuals early in their disease trajectory for targeted management to halt or modify progression.