Phenotyping helps identify the underlying inflammatory mechanism driving a patient's asthma, most notably distinguishing Type 2 high from non-Type 2 disease. This distinction increasingly guides treatment decisions, particularly around eligibility for targeted biologic therapies in severe asthma. Phenotyping typically incorporates blood eosinophil count, exhaled nitric oxide and allergic sensitisation status. A clearer phenotypic understanding supports more individualised and effective treatment selection.

Type 2 inflammation refers to an immune pathway involving cytokines such as interleukin-4, interleukin-5 and interleukin-13, which drive eosinophilic and allergic airway inflammation. A substantial proportion of patients with severe asthma have a Type 2 high inflammatory profile. Identifying this pattern is clinically relevant because several biologic therapies specifically target components of this pathway. Assessment typically combines clinical history with relevant biomarker testing.

Referral is generally appropriate for patients with poorly controlled asthma despite optimised inhaled therapy, or those requiring frequent oral corticosteroid courses. Specialist assessment can confirm the diagnosis, evaluate for relevant comorbidities and consider phenotyping to guide further treatment options. Early referral for uncontrolled severe asthma can reduce cumulative exposure to systemic corticosteroids and their associated risks. Local respiratory or allergy guidelines can support decisions on referral timing.