Asthma and chronic obstructive pulmonary disease can be difficult to differentiate, and this will remain an important clinical dilemma for the forseeable future, respiratory experts have claimed.

Speaking at Clinical Consensus on COPD, an international forum held in London, UK, last week, Ronald Buhl (Mainz University Hospital, Germany) said that clinicians must distinguish the two diseases at an early stage as their morbidity, treatment, and prognosis differ.

But he acknowledged that some cases can be difficult to diagnose.

"To diagnose patients with a clear-cut clinical history is no problem," he told delegates at the conference. But he said it is his "firm belief" that there are patients with signs of both diseases.

"If you're not sure, treat the patient as if he or she had asthma to be on the safe side," he said.

"COPD is characterized by airflow limitation that is not fully reversible, is usually progressive, and is associated with an abnormal inflammatory response of the lungs to noxious particles or gases, particularly cigarette smoke," he explains in the accompanying abstract.

"Asthma is characterized by chronic airway inflammation associated with airway hyper-responsiveness that leads to recurrent episodes of wheezing, breathlessness, chest tightness, and coughing," he adds.

These functional abnormalities are usually reversed by treatment with bronchodilators with or without corticosteroids.

However, patients with asthma who are exposed to noxious particles, such as cigarette smoke, may develop fixed airway limitation and both "asthma-like" and "COPD-like" symptoms, he explains.

"In some individuals who develop chronic respiratory symptoms and fixed airflow limitation it may be difficult to differentiate the two diseases using current lung function testing and imaging techniques," he continues, "and it is assumed that asthma and COPD exist."

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