BACKGROUND: Asthma and chronic obstructive pulmonary disease (COPD) are obstructive airway diseases related to chronic airway inflammation. However, it is known that the overlapped syndrome of the two diseases exists in real practice.

OBJECTIVES: The purpose of this study was to investigate the reality of an intermediate type between asthma and COPD when diagnosed by physicians in Korea.

METHODS: The study involved 633 Korean patients with asthma, 157 with COPD, and 41 with an intermediate type. The latter group consisted of patients with clinically mixed or overlapping characteristics of asthma and COPD. The diagnoses were dependent on physicians' clinical decision. We analyzed the clinical differences among those three groups.

RESULTS: There were differences among the three groups in age, gender, atopy, and BMI. Differences in smoking status, including percentages of current smokers, duration of smoking, and number of cigarettes smoked per day, were also observed. Prebronchodilator FEV₁ (%), FVC (%), and FEV₁/FVC ratio (%) gradually decreased from the asthma group to the intermediate type group to the COPD group. Positivity of postbronchodilator response, increase of FEV₁ (%) and postbronchodilator FEV₁/FVC ratio also showed gradual patterns. For emergency room visits and hospital admissions, frequencies were lowest in the asthma group, higher in the intermediate type group, and highest in COPD patients. All p-values were statistically significant (<0.001).

CONCLUSIONS: We have identified and characterized an intermediate type, lying between asthma and COPD in clinical characteristics. Further investigations are required to determine whether these three conditions are part of the chronic obstructive airway diseases spectrum or are rather distinct clinical entities.