Clinically relevant subgroups in COPD and asthma

Abstract

As knowledge of airways disease has grown, it has become apparent that neither chronic obstructive pulmonary disease (COPD) nor asthma is a simple, easily defined disease. In the past, treatment options for both diseases were limited; thus, there was less need to define subgroups. As treatment options have grown, so has our need to predict who will respond to new drugs. To date, identifying subgroups has been largely reported by detailed clinical characterisation or differences in pathobiology. These subgroups are commonly called "phenotypes"; however, the problem of defining what constitutes a phenotype, whether this should include comorbid diseases and how to handle changes over time has led to the term being used loosely. In this review, we describe subgroups of COPD and asthma patients whose clinical characteristics we believe have therapeutic or major prognostic implications specific to the lung, and whether these subgroups are constant over time. Finally, we will discuss whether the subgroups we describe are common to both asthma and COPD, and give some examples of how treatment might be tailored in patients where the subgroup is clear, but the label of asthma or COPD is not.

FIGURE 1

Chronic obstructive pulmonary disease subgroups without clear treatment implications. The figure shows the subgroups with clear prognostic implications for patients that are clinically relevant, but where therapeutic strategies are as yet unclear. The directions of the arrows indicate the probable direction of the association, e.g. patients with more frequent exacerbations are less likely to survive. The direction of association of bacterial colonisation and bronchiectasis is not clear; thus, a bidirectional arrow is shown.

FIGURE 2

Schematic diagram of the shared subgroups between asthma and chronic obstructive pulmonary disease (COPD). The figure shows phenotypes that are recognised in both conditions. The placement/colour of the shapes indicates the degree to which they are recognised in asthma and COPD. ABPA: allergic bronchopulmonary aspergillosis.