After outpatient clinic visit, asthmatic patients with worsening of symptoms (including dyspnea, wheezing, chest tightness, cough, activity limitation, awaken in the midnight due to discomfort) and are diagnosed of acute exacerbation by physician, will be recruited. The patients are asked to record symptoms using asthma symptom diary (ASD) with home spirometry simultaneously for 14 days.

Visit 1 (day 1)

All patients will be evaluated the following:

1. Record the patients' demographics (age, gender, race), baseline characteristics, comorbidities, health care resources use (visits, lab tests, hospitalization and cost), pharmacological and non-pharmacological treatments
2. Blood sampling for eosinophils, eosinophil cationic protein (ECP) and immunoglobulin E (IgE) as clinically indicated (if no data available within one year for the last two)
3. The study assistant will introduce to the patient how to manipulate the home spirometry and its app, and to record the daily asthma symptoms by using the ASD on the mobile phone.

Visit 2 (day 15) All patients will be arranged outpatient clinic follow up 2 weeks later from the first visit. The outpatient clinic physician will check the home spirometry report and ASD symptom score in the past 2 weeks, and have a well explanation of these results.

Statistical analysis The usage of digital function including input ASD, and the lung function from portable spirometer in study arm will be demonstrated by descriptive statistics.

Inclusion Criteria:

• Age 20 to 75 years old asthmatic patients under regular treatment for at least 3 months.
• Patients in asthma acute exacerbation (symptoms onset within 1 week) and received oral corticosteroid for more than 3 days.

Exclusion Criteria:

• Refuse to provide inform consent.
• Patients with chronic obstructive pulmonary disease.
• Patients who receive more than 20mg prednisone or equivalent dose per day.
• Patients who are incapable of using smart phone.