[Diagnostic differences in asthma and chronic obstructive pulmonary disease].

Although both asthma and chronic obstructive pulmonary disease (COPD) are characterized as obstructive lung disease, their pathophysiologies are quite different. Characteristics of asthma include chronic airway inflammation, airway narrowing with reversibility, and responsiveness of airways. Cough, wheezing, and dyspnea and variability in these symptoms are also characteristic features of asthma. Because there are no definite diagnostic criteria, multidisciplinary consideration is necessary when diagnosing asthma. On the other hand, COPD is characterized by persistent airflow limitation which is usually progressive. It is associated with noxious particles or gasses, typically cigarette smoking, and subsequent chronic inflammation of the airway and lungs. Nonreversible airflow limitation is a characteristic feature, and exertional dyspnea, chronic cough, and sputum are typical symptoms. Diagnostic criteria are relatively simple: post bronchodilator FEV1/FVC < 70%, and no other reason for airflow limitation. Recently, overlap syndrome, with features of both asthma and COPD, is drawing attention. When treating elderly patients with asthma who have persistent airway limitation or patients with COPD who show variability in symptoms and reversibility of lung function, the possibility of overlap syndrome should be considered. The prevalence of overlap syndrome seems to be high in general practice, so the introduction of practical criteria for the diagnosis and a proper guide for therapies is expected.