Asthma Diagnosis and Treatment in UK Primary Care 2026: What the BTS/NICE/SIGN Guideline (NG245) Changed

In November 2024, the British Thoracic Society, NICE, and SIGN published a single joint asthma guideline — NG245 — replacing three separate sets of advice that had drifted apart for years. Two changes stand out for primary care, and both are large: how asthma is diagnosed, and what the reliever inhaler now contains.

This post covers what changed and what it means at the appointment level in 2026. It is written for UK GPs, GP registrars, practice nurses, GP pharmacists, and trainees. The guideline and the BNF remain the authoritative references; this post summarises and links, it does not substitute for clinical judgement.

Diagnosis now leads with inflammation

The old reflex was to reach for spirometry first. NG245 reorders the pathway around markers of eosinophilic airway inflammation.

For adults aged 16 and over with a suggestive history, the first step is a blood eosinophil count or a FeNO measurement. If the eosinophil count is above the laboratory reference range, or FeNO is 50 ppb or more, asthma can be diagnosed at that point. Where those are not diagnostic, testing continues in sequence — bronchodilator reversibility, peak expiratory flow variability, and, if still unresolved, a bronchial challenge.

The principle underneath is worth stating: no single test is a gold standard. Spirometry with reversibility has high specificity but low sensitivity in adults; peak flow variability is specific but insensitive; FeNO is specific but loses sensitivity in smokers and in obesity. The pathway is built to be followed in order, not cherry-picked — a negative early test does not rule asthma out, it moves you to the next test.

For primary care, the practical question this raises is access. A pathway that leads with FeNO and eosinophils depends on those tests being available, and that availability is uneven. Knowing your local route to FeNO is now part of being able to diagnose asthma to guideline standard.

The reliever has changed

The bigger shift for day-to-day prescribing is the end of the SABA-only reliever for people aged 12 and over.

The evidence is hard to argue with: over-reliance on a short-acting beta agonist, without an inhaled corticosteroid, is associated with worse outcomes — and it was a recurring theme in the National Review of Asthma Deaths. NG245 responds by putting an anti-inflammatory component into the reliever itself.

AIR — anti-inflammatory reliever. For people aged 12 and over with infrequent symptoms, starting therapy is now a low-dose inhaled corticosteroid/formoterol inhaler taken as needed, rather than a SABA alone. One as-needed inhaler delivers both treatment and relief.

MART — maintenance and reliever therapy. For more persistent symptoms, the step up is a single inhaled corticosteroid/formoterol inhaler used both as regular maintenance and as the reliever. The patient carries one device, not two. The economic analysis behind the guideline found AIR and MART to be more effective and less costly than the traditional inhaled corticosteroid plus separate SABA approach.

From November 2025, a budesonide/formoterol dry powder inhaler was also licensed for MART in children aged 6 to 11, extending the approach to younger children. The age-specific pathways differ, so the guideline should be consulted directly for the under-16 and under-12 detail.

What this means for practice

Two pieces of work follow from the guideline, and neither needs a new clinic.

The first is inhaler review. Patients still on a SABA-only reliever are the priority cohort — a search for high SABA issue without a preventer surfaces them quickly, and each is a conversation about switching to an anti-inflammatory reliever. The second is diagnostic discipline: a documented, sequential pathway rather than a single test, and a clear local route to FeNO so that diagnosis is not stalled by access.

The reliever-in-the-pocket habit is decades old. Changing it is the patient-facing work the guideline creates — and it is where the outcome benefit actually sits.

A note on what this post is — and is not

This is a guideline summary for awareness. It is not a substitute for NICE NG245, the BNF, or local prescribing and diagnostic policy. The age-specific pathways, test cut-offs, and licensed products should be confirmed against the guideline and the BNF before applying them. Clinical decisions remain the responsibility of the treating clinician.

The Monday Clinical Brief publishes weekly summaries of the most important new papers and guideline updates across 31 UK medical specialties — including guideline changes like this one. We surface them, summarise them, and link to them, so practice-changing material does not get missed in a busy clinical week.

Related reading

• How to keep up with the medical literature — the wider problem of staying current when guidelines move this fast.
• NICE NG28 February 2026: SGLT2 inhibitors first-line for type 2 diabetes — another major UK primary-care guideline change to keep on the radar.
• Statins and CVD prevention in UK primary care 2026 (NICE NG238) — the lipid pathway, reframed around shared decisions.

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