Asthma attacks which are moderate-to-severe are typically treated with corticosteroids, but the optimal treatment duration is unknown and treatment responses can be variable. Inadequate treatment may compromise recovery, but increased exposure to corticosteroids is, in turn, associated with drug-related adverse effects.

There is a need for a biomarker to guide duration of corticosteroid treatment in asthma attacks. One such candidate biomarker is the blood eosinophil count, which may predict steroid-responsiveness. We hypothesize that the blood eosinophil count can potentially be used as a biomarker to guide the duration of corticosteroids in moderate-to-severe asthma attacks.

This study will recruit individuals hospitalized for asthma attack. Participants will be randomized to standard care or blood-eosinophil guided systemic corticosteroid therapy. Subjects in the standard arm will receive oral corticosteroids for a total of 5 days. Subjects in the blood-eosinophil guided arm will receive oral corticosteroids for a total of 5 days if admission eosinophil count is ≥ 0.300 x 10^3/µL, and receive 3 days of oral corticosteroids if the admission blood eosinophil is < 0.300 x 10^3/µL. The rate of treatment failure will be compared between these two groups.

Inclusion Criteria:

1. Age ≥ 21 years old
2. Admitted for acute exacerbation of asthma and have received ≤ 3 days of systemic corticosteroids
3. Have a had a blood eosinophil count (as part of routine clinical care) drawn before administration of systemic corticosteroid
4. Have not taken SCS within 7 days prior to presentation to hospital

Exclusion Criteria:

1. Concomitant pneumonia
2. Admission to high-dependency/intensive care unit, or requirement for invasive/noninvasive mechanical ventilation
3. Eosinophilia due to other known causes (eosinophilic granulomatosis and polyangiitis, parasitic infections, malignancy)
4. Other concomitant respiratory conditions e.g. chronic obstructive pulmonary disease, bronchiectasis
5. Those on anti-IL5 or anti-IL5R treatment
6. Pregnant subjects
7. Subjects who are already on an investigational drug or has been participating in another clinical study with an investigational product within the last 6 months
8. Subjects deemed by investigators to have a life expectancy of < 12 months (any cause)
9. Prisoners