NICE vs BTS Guidance for Sign Management of Asthma (2025)

This page compares the 2025 National Institute for Health and Care Excellence (NICE) guideline NG239 and the British Thoracic Society (BTS)/Scottish Intercollegiate Guidelines Network (SIGN) guideline 158 for the management of asthma in adults, young people, and children. Both guidelines aim to standardise and improve asthma care, but they differ in several key areas, including diagnostic criteria, treatment thresholds, and escalation pathways. This comparison is intended to help clinicians navigate these differences and apply the guidance appropriately in practice.

Summary of Agreement and Differences

NICE and BTS/SIGN guidelines share the common goal of improving asthma outcomes through evidence-based management. They agree on fundamental principles such as the importance of accurate diagnosis, the role of inhaled corticosteroids (ICS) as first-line controller therapy, and the need for personalised asthma action plans. However, significant differences exist, particularly in diagnostic approaches. NICE recommends objective testing with spirometry and bronchodilator reversibility or FeNO as a first step for adults, while BTS/SIGN places greater emphasis on clinical assessment and a trial of treatment. For treatment, NICE advocates a more structured step-up approach, whereas BTS/SIGN allows for more clinician discretion. Understanding where the guidelines converge and diverge is essential for safe and effective patient care.

Key Differences Between NICE and BTS/SIGN Asthma Guidelines

Area	NICE NG239 (2025)	BTS/SIGN 158 (2025)
Diagnosis & Criteria	Emphasis on objective confirmation. For adults, recommends spirometry with bronchodilator reversibility (BDR) or FeNO testing as initial investigations. A positive test supports diagnosis.	Diagnosis is primarily clinical, based on symptomatic history and evidence of variable airflow obstruction. Objective tests are used to support but are not always mandatory for initial diagnosis.
Treatment Thresholds	Recommends starting regular inhaled corticosteroids (ICS) for patients with asthma symptoms that require short-acting beta-2 agonists (SABA) more than twice a week, or who have had an exacerbation in the last two years.	Suggests considering ICS if symptoms occur more than twice a week, but allows for more clinical judgement regarding frequency and impact on quality of life.
Investigations	FeNO is a key diagnostic tool, especially when diagnosis is uncertain. Spirometry is strongly recommended for all adults at presentation.	FeNO is recommended as an option to support diagnosis, but spirometry may be deferred if clinical features are strongly suggestive and treatment response is good.
First-line Treatment	Low-dose ICS as the first maintenance therapy for adults and children over 5. A SABA is the reliever.	Low-dose ICS as first-line controller. BTS/SIGN also discusses the option of leukotriene receptor antagonists (LTRA) in specific cases, such as in patients unable to use ICS.
Escalation	Structured step-up: from low-dose ICS to low-dose ICS/LABA combination. Further steps include medium-dose ICS/LABA and add-on therapies like LTRAs or theophylline.	Similar stepwise approach but with more flexibility. Suggests considering increasing ICS dose before adding LABA, or vice-versa, based on patient phenotype and response.
Follow-up	Structured review within 3 months of treatment initiation or change, then annually. Focus on symptom control, inhaler technique, and adherence.	Regular review is recommended, but the timing is less prescriptive, focusing on clinical need, stability, and patient education.

Detailed Analysis of Diagnostic Approaches

The divergence in diagnostic methodology represents one of the most significant practical differences between the two guidelines. NICE's 2025 update reinforces a shift towards objective, biomarker-driven diagnosis to reduce misdiagnosis rates. The guideline specifies that for adults (aged 17 and over), spirometry with bronchodilator reversibility testing should be performed. A positive result is defined as an improvement in FEV1 of 12% or more and 200ml or more after bronchodilator administration. Alternatively, fractional exhaled nitric oxide (FeNO) testing can be used, with a level of 40 parts per billion or more supporting a diagnosis of asthma. This approach is particularly recommended when the clinical history is suggestive but not definitive.

BTS/SIGN, while acknowledging the value of these tests, maintains a more traditional stance centred on clinical probability. The guideline advises that a diagnosis can be made based on a characteristic pattern of symptoms (wheeze, breathlessness, chest tightness, cough) and documented variable airflow obstruction. Objective tests are crucial for confirmation but may follow a therapeutic trial in primary care settings where access to spirometry might be delayed. This difference can lead to variations in practice: a clinician following NICE might refer for spirometry before initiating long-term treatment, while one following BTS/SIGN might start a low-dose ICS trial based on history alone, reviewing the response after a few weeks. Both approaches have merits; the NICE method aims for diagnostic certainty from the outset, while the BTS/SIGN method prioritises early symptom relief while investigations are arranged.

Treatment Escalation: A Comparative Deep Dive

When asthma remains uncontrolled on initial therapy, the pathways for escalation highlight another area of nuanced difference. NICE NG239 outlines a clear, sequential step-up model. Step 1 is a SABA reliever only for intermittent symptoms. Step 2 introduces regular low-dose ICS. If control is inadequate, Step 3 involves moving to a low-dose ICS/long-acting beta-2 agonist (LABA) combination inhaler for maintenance and reliever therapy (MART) where applicable, or a standard fixed-dose regimen. Steps 4 and 5 involve increasing the ICS dose to medium or high dose within the combination inhaler and considering add-on therapies such as LTRAs, slow-release theophylline, or tiotropium.

BTS/SIGN Guideline 158 offers a similar framework but incorporates greater flexibility, often referred to as a "bifurcated" or "phenotype-driven" approach. At the point of escalation from low-dose ICS (Step 2), the guideline presents options. The clinician can either increase the dose of ICS to a moderate level or add a LABA. The choice is intended to be informed by the patient's phenotype. For example, a patient with predominantly eosinophilic inflammation (suggested by high FeNO or blood eosinophils) might benefit more from a higher ICS dose, whereas a patient with exercise-induced symptoms might respond better to a LABA. This flexibility requires a deeper understanding of asthma phenotypes but allows for more personalised care. NICE's more linear approach provides a standardised, easy-to-follow algorithm that may be preferable in generalist settings.

Special Populations and Considerations

Both guidelines address specific patient groups, but with varying emphasis. In children under 5, diagnosis is particularly challenging. NICE recommends a clinical diagnosis based on symptom response to a 2-month trial of ICS, as objective testing is unreliable in this age group. BTS/SIGN provides similar advice, stressing the importance of re-evaluating the diagnosis periodically. For pregnant women, both guidelines emphasise the critical importance of maintaining good asthma control for maternal and fetal health, with ICS as the preferred controller medication. Neither recommends withholding necessary treatment.

A notable difference emerges in the approach to occupational asthma. NICE includes specific recommendations for asking about occupational exposures in every adult with new-onset or worsening asthma and provides guidance on referral for specialist assessment. BTS/SIGN also covers occupational asthma but integrates it within the broader diagnostic section. For severe asthma, both guidelines advise referral to a specialist centre, but NICE provides more detailed criteria for referral, including the need for high-dose ICS plus a second controller, or repeated courses of oral corticosteroids.

Safety Notes and Common Pitfalls

Adherence to either guideline requires vigilance to avoid common failure modes. A significant risk arises from misdiagnosis. Relying solely on clinical history without objective testing (contrary to NICE emphasis) can lead to over-diagnosis of asthma or missing alternative diagnoses like vocal cord dysfunction. Conversely, delaying treatment while awaiting investigations in a symptomatic patient (a strict interpretation of NICE) could be unsafe. The most likely change to catch clinicians out is the differing emphasis on FeNO; a clinician accustomed to BTS/SIGN may underutilise this test, potentially missing eosinophilic inflammation. Another critical safety point is SABA over-reliance. Both guidelines warn against this, but NICE is more explicit in linking frequent SABA use to the need for initiating or stepping up controller therapy. When escalating treatment, ensure the correct inhaler technique is established and adherence is assessed before labelling a treatment as ineffective.

Additional safety considerations include the risk of steroid phobia leading to poor adherence to ICS, which must be addressed through patient education. There is also a potential pitfall in the transition from paediatric to adult services, where management strategies may change; clear communication is essential. Finally, clinicians should be aware of the signs of severe or life-threatening asthma exacerbations, which are defined similarly in both guidelines, and have a low threshold for emergency referral.

Documentation Cues for Clinical Practice

Clear documentation is essential, especially when deviating from a specific guideline. When following NICE guidance, record the results of objective tests (spirometry, FeNO) used to confirm the diagnosis. If a decision is made to treat empirically based on strong clinical suspicion (aligning more with BTS/SIGN), document the rationale clearly, e.g., "High pre-test probability based on typical history; treatment initiated pending spirometry access." When choosing an escalation pathway that differs from the preferred sequence in one guideline, note the clinical reasoning, such as "Patient intolerant of LABA; LTRA added per BTS/SIGN option despite being on Step 2." Always document discussions with the patient about their treatment plan, including their understanding and agreement. This demonstrates a reasoned clinical decision-making process, whether strictly adhering to one guideline or synthesising elements from both.

Specific items to document include: baseline assessment of symptom control (e.g., using the Asthma Control Questionnaire or a simple symptom diary), inhaler technique check and any education provided, patient's personal best peak flow (if used), and the details of the written asthma action plan issued. For each review, record the current treatment step, any changes made, and the reason for the change. This creates a clear audit trail that supports continuity of care and clinical governance.

Sources and Further Reading

• NICE Guideline NG239: Asthma: diagnosis, monitoring and chronic asthma management. Published: March 2025.
• BTS/SIGN Guideline 158: British Guideline on the Management of Asthma. Updated: July 2025.

Please note that guidelines are subject to change. Always refer to the official sources for the most current versions. For complex cases or diagnostic uncertainty, early referral to a respiratory specialist is recommended.