Differentiating Asthma from COPD

Whilst asthma and chronic obstructive pulmonary disease (COPD) are different diseases they cause similar symptoms, which can present a challenge in identifying which disease a patient is suffering from. A study by Tinkelman et al (2006) showed that among subjects with a spirometry-based study diagnosis of COPD, 121 (51.5%) reported a prior diagnosis of asthma without concurrent chronic bronchitis or emphysema (CBE) diagnosis, 89 (37.9%) reported a prior diagnosis of CBE, and 25 (10.6%) reported no prior diagnosis of obstructive lung disease.

There are, however, some important distinctions between asthma and COPD. COPD causes chronic symptoms and narrowed airways which do not respond to treatment to open them up. In the case of asthma the constriction of the airways through inflammation tends to come and go and treatment to reduce inflammation and to open up the airways usually works well.

COPD is more likely than asthma to cause a chronic cough with phlegm and is rare before the age of 35 whilst asthma is common in under-35s. Disturbed sleep caused by breathlessness and wheeze is more likely in
cases of asthma, as is a history of allergies, eczema, and hay fever. Differentiating between COPD and asthma requires a history of both symptoms and spirometry. The spirometry history should include post bronchodilator measurements, the degree of reversibility and, ideally, home monitoring which gives a history of diurnal variation.

Many patients have features of both COPD and asthma ‘asthma-COPD overlap’ (ACO) however these terms do not refer to a single disease entity. The clinical phenotypes in these patients are likely caused by a range of different underlying mechanisms