A Study to Compare Severe Asthma Patients Who Start Biologics and Who do Not Start (PROSPECT)

Inclusion Criteria: 1. Confirmed asthma diagnosis 2. Using high-dose ICSa and 2nd controllerb more than 3 months before registration 3. Uncontrolled asthma which constitutes one or more of 1) Poor symptom control: ACQ-5≧1.5 or ATC\<20 2) Frequent exacerbations: at least 2 asthma exacerbations in the 12 months prior to the registration 3) Airflow obstruction: FEV1 before taking bronchodilator \<80% predicted (FEV1/FVC less than the lower limit of normal) C 4. Investigators judges the necessity of biologic treatment for his/her asthma treatment and the patients are explained the situation by the investigators. 5. Patients deemed capable of visiting their study site next 24 months regularly 6. Patients from whom written consent to participate in this study has been obtained 7. Patients≧20 years old at obtaining consent Exclusion Criteria: 1. Participated in other interventional studies such as clinical trials, etc within the last 8 weeks. 2. Are using biologics at registration 3. Diagnosed as COPD 4. Plan the BT therapy near future 5. Receipt of any marketed or investigational biologics within 5 months before the registration 6. Any disorder, including, but not limited to, cardiovascular, gastrointestinal, hepatic, renal, neurological, musculoskeletal, infectious, endocrine, metabolic, haematological, psychiatric, or major physical impairment that is not stable in the opinion of the investigator and could: * Affect the safety of the patient throughout the study * Influence the findings of the studies or their interpretations * Impede the patient's ability to complete the entire duration of study.