Synopsis
Distinguish modifiable difficult asthma from genuinely severe disease, recognise eosinophilic and broader type 2 traits, and refer safely for specialist phenotype-led treatment.
- Difficult asthma remains uncontrolled for any reason; severe asthma is the smaller subset that stays uncontrolled despite confirmed diagnosis, optimised adherence, technique, exposures, comorbidity and high-intensity treatment.
- Before adding specialist drugs, revisit whether symptoms are asthma: inducible laryngeal obstruction, dysfunctional breathing, obesity, cardiac disease, bronchiectasis and anxiety can coexist or mimic poor control.
- Count attacks, urgent care, systemic corticosteroid courses and functional restriction; a symptom score alone can miss serious future risk.
- Pharmacy refill data, direct inhaler observation and a non-judgemental adherence discussion are core investigations, not administrative extras.
- Blood eosinophils and FeNO are treatment-responsive and biologically variable; a low result during systemic corticosteroid exposure does not reliably exclude type 2 disease.
- Biologic eligibility is drug-specific and governed by current NICE technology appraisals, licensed indications and specialist commissioning pathways rather than a single universal eosinophil cut-off.
- Biologics are add-on maintenance therapies, not rescue treatment; inhaled corticosteroid must continue and oral corticosteroid reduction must be supervised.
- Frequent short-acting beta2 agonist use, repeated oral corticosteroid bursts and poor collection of preventer inhalers are high-risk signals requiring active review.
- Look for allergic bronchopulmonary aspergillosis, eosinophilic granulomatosis with polyangiitis and parasitic or haematological causes when eosinophilia or systemic features are disproportionate.
- Refer to a specialist severe-asthma service when diagnosis or phenotype is uncertain, attacks continue despite optimisation, maintenance oral corticosteroid is needed or a biologic may be appropriate.
Key red flags
Repeated systemic corticosteroid courses, emergency attendance, admission, previous ventilation, rising reliever use or abrupt loss of control predicts future harm even when the person appears comfortable at a planned review.
Neuropathy, purpura, renal or cardiac features, constitutional illness, pulmonary infiltrates or marked persistent eosinophilia should trigger urgent assessment for vasculitis, infection, drug reaction, haematological disease or another systemic cause.
Investigation priorities
Confirm variable airway disease before labelling severe asthma.
Management branches
Symptoms or attacks persist despite apparently high-intensity asthma treatment.
- Reconstruct the diagnosis from symptom pattern, objective variable airflow evidence, previous attacks and response, considering airway and non-airway mimics.
- Observe every inhaler, reconcile prescriptions with collections and daily use, and switch device or education strategy when delivery is unreliable.
- Identify smoke, vaping, occupational or allergen exposure and treat relevant rhinitis, obesity, sleep disorder, dysfunctional breathing or laryngeal dysfunction.
- Optimise NICE-recommended inhaled treatment and an action plan, then reassess attacks, control and lung function over an appropriate interval before calling disease severe.
Key medicines
High-intensity inhaled corticosteroid-formoterol maintenance and reliever therapyUse the current NICE step and exact locally selected inhaler strength, maintenance schedule and as-needed limit after specialist technique and adherence review.Only licensed ICS-formoterol products and regimens should be used for MART. High use requires prompt review; monitor local and systemic corticosteroid effects, and do not add a separate LABA-containing inhaler inadvertently.
Mepolizumab for eligible severe eosinophilic asthmaFor adults and adolescents, 100 mg subcutaneously once every four weeks as specialist-initiated long-term add-on treatment under current NICE criteria.Not for acute attacks and not a reason to stop inhaled or oral corticosteroid abruptly. Confirm product, age and commissioning eligibility; monitor hypersensitivity, infection context and agreed clinical response, reviewing ongoing need at least annually.