Severe therapy-resistant asthma has been defined as "asthma which requires treatment with high dose inhaled corticosteroids (ICSs) plus a second controller (and/or systemic corticosteroids) to prevent it from becoming 'uncontrolled' or which remains 'uncontrolled' despite this therapy". Patients who usually present with 'difficult-to-treat asthma' should first be assessed to determine whether he/she has asthma with the exclusion of other diagnoses and if so, whether the asthma can be classified as severe therapy-resistant. This necessitates an assessment of adherence to medications, confounding factors, and comorbidities. Increasingly, management of severe therapy-resistant asthma will be helped by the determination of phenotypes to optimize responses to existing and new therapies. Severe asthma patients are usually on a combination of high dose ICS and long-acting β-agonist (LABA) and, in addition, are often on a maintenance dose of oral corticosteroids. Phenotyping can be informed by measuring blood eosinophil counts and the level of nitric oxide in exhaled breath, and the use of sputum granulocytic counts. Severe allergic asthma and severe eosinophilic asthma are two defined phenotypes for which there are efficacious targeted biologic therapies currently available, namely anti-immunoglobulin E (IgE) and anti-interleukin (IL)-5 antibodies, respectively. Further progress will be realized with the definition of noneosinophilic or non-T2 phenotypes. It will be important for patients with severe asthma to be ultimately investigated and managed in specialized severe asthma centers.
Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.