Asthma-COPD Overlap Syndrome : a review of current knowledge and future directions

Abstract

Asthma and chronic obstructive pulmonary disease are common diseases both characterised by airflow obstruction. Over recent decades the prevailing belief was that asthma and COPD were distinct diseases that can be easily distinguished and require different treatments. This stimulated basic scientific research aimed at obtaining a better understanding of both diseases, particularly COPD that had been neglected. The downside of this approach was that it resulted in the exclusion of patients from clinical trials that exhibited features of both diseases. However, it has been increasingly recognised that these patients are common in everyday clinical practice and that their exclusion from clinical trials meant that therapeutic decisions were not evidence based. The concept of the asthma COPD overlap syndrome is an attempt to develop diagnostic criteria for patients with features of both asthma and COPD. This is a necessary starting point from which to design studies to investigate the clinical features, aetiology, pathophysiology and prognosis of these patients, and ultimately determine treatment strategies. However, from the outset the concept of asthma COPD overlap syndrome has been controversial and has not gained universal acceptance. In this review we will describe current definitions and concepts of the asthma COPD overlap syndrome and explore how our understanding of this syndrome may develop in the future.