Table 1.

JRS diagnostic criteria for ACO.

Basic Characteristics
Post-bronchodilator FEV1/FVC < 70% in individuals 40 years of age or older
Exclusion of other pulmonary diseases by chest X-ray and other relevant techniques
Features of BA	Features of COPD
2 items from 1–3 apply or 1 item from 1–3 and 2 items from 4 apply.	1 item from 1–3 apply.
1. Variable (diurnally, daily, seasonally) or paroxysmal respiratory symptoms (cough, sputum, dyspnea)	1. Smoking history (≥10 pack-years) or same level of air pollution exposure
2. BA diagnosis history under 40 years	2. Presence of low attenuation area showing emphysematous changes on chest CT
3. FeNO > 35 ppb	3. Impaired pulmonary diffusing capacity (DLCO < 0.8 or DLCO/VA < 0.8)
4-1. Complication of allergic rhinitis
4-2. Bronchodilator response of FEV1 ≥ 200 mL and 12% from baseline
4-3. Peripheral blood eosinophil count > 5% or 300 cells/μL
4-4. High levels of IgE (total IgE or specific IgE against perennial inhalant antigens)

JRS, the Japanese Respiratory Society; ACO, asthma–COPD overlap; BA, bronchial asthma; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 s; FVC, forced vital capacity; D_LCO, diffusing capacity of the lung for carbon monoxide; FeNO, fractional exhaled nitric oxide; IgE, immunoglobulin E.