NICE vs BTS/SIGN: Management of Pulmonary Embolism (2025)

This guide provides a comparative overview of the National Institute for Health and Care Excellence (NICE) guideline NG158 and the British Thoracic Society (BTS)/Scottish Intercollegiate Guidelines Network (SIGN) guideline 158 for the management of acute pulmonary embolism (PE). It is designed to help clinicians understand the key similarities and differences in diagnostic pathways, treatment strategies, and management of special situations, facilitating informed decision-making in UK clinical practice.

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Diagnosis and Initial Assessment

Both guidelines prioritise rapid risk stratification but differ in their diagnostic algorithms, particularly in the use of clinical probability scores.

NICE NG158 (Published 2020, last updated March 2025)

Clinical Probability Assessment: Recommends the use of a two-level PE Wells score (PE likely vs PE unlikely) for all patients.
D-dimer Use: D-dimer testing is recommended only for patients in whom PE is considered unlikely (Wells score ≤4). A negative D-dimer excludes PE without the need for imaging.
Imaging: For patients with a 'PE likely' Wells score (>4) or a positive D-dimer in the 'unlikely' group, NICE recommends immediate computed tomography pulmonary angiography (CTPA). Ventilation-perfusion (V/Q) scanning is a second-line option if CTPA is contraindicated.
Key Takeaway: Streamlined pathway that restricts D-dimer use to a specific low-risk group, aiming to reduce unnecessary imaging.

BTS/SIGN 158 (Published 2019, reviewed 2024)

Clinical Probability Assessment: Uses a modified two-level Wells score, but its application is more flexible. BTS places a stronger emphasis on clinical gestalt, especially in secondary care, acknowledging that experienced clinicians may override a formal score.
D-dimer Use: Recommends D-dimer testing for patients with low or intermediate clinical probability. A negative, age-adjusted D-dimer can exclude PE in these patients.
Imaging: Similar to NICE, CTPA is first-line. BTS provides more detailed guidance on the use of V/Q SPECT as a preferred isotopic technique and discusses the role of bilateral leg ultrasound as an alternative diagnostic method in patients with suspected DVT where thoracic imaging is high-risk.
Key Difference: BTS offers greater flexibility in pre-test probability assessment and explicitly endorses the age-adjusted D-dimer (threshold = age × 10 µg/L in patients >50 years), which increases specificity in older adults.

Treatment and Anticoagulation Strategies

The guidelines are largely aligned on treatment principles but have nuanced differences in duration and agent choice.

Initial and Primary Treatment

Shared Position: Both guidelines strongly recommend Direct Oral Anticoagulants (DOACs) over vitamin K antagonists (VKAs, e.g., warfarin) for the vast majority of patients with confirmed PE.

NICE: States that apixaban or rivaroxaban should be offered as first-line treatment.
BTS: Recommends DOACs (apixaban, dabigatran, edoxaban, rivaroxaban) as the preferred option, noting their efficacy, safety, and convenience.
Key Difference: BTS provides more extensive discussion on the management of cancer-associated thrombosis (CAT), recommending DOACs (apixaban, edoxaban, rivaroxaban) for most solid tumours without high bleeding risk or drug interactions. NICE also recommends DOACs for CAT but advises caution with rivaroxaban and edoxaban in upper GI cancers and considers LMWH (low molecular weight heparin) as an effective alternative.

Treatment Duration

Both Guidelines recommend a minimum of 3 months of therapeutic anticoagulation for a first PE provoked by a major transient/reversible risk factor.
For unprovoked PE, both advise considering extended anticoagulation after 3 months based on the patient's risk of recurrence versus bleeding risk.
BTS provides a more detailed framework for this decision, explicitly incorporating the use of the HERDOO2 rule to identify women with unprovoked PE who may safely discontinue anticoagulation.

Management of Special Situations

High-Risk (Massive) PE

NICE: Strongly recommends systemic thrombolysis for patients with high-risk PE and haemodynamic instability (e.g., sustained hypotension), unless there are major contraindications.
BTS: Similarly recommends thrombolysis but provides more detailed guidance on rescue therapies if thrombolysis fails or is contraindicated, including catheter-directed techniques and surgical embolectomy, outlining the criteria for transfer to a specialist centre.

Submassive (Intermediate-High Risk) PE

This is a major area of divergence.
- NICE: Does not recommend routine thrombolysis for patients with intermediate-risk PE. Recommends close monitoring and standard anticoagulation.
- BTS: Suggests that thrombolysis may be considered on a case-by-case basis for selected patients with intermediate-high risk PE (e.g., significant RV dysfunction and elevated cardiac biomarkers) and a low bleeding risk. This is a key practical difference.

Pregnancy

Both Guidelines recommend diagnostic imaging (with radiation dose optimisation) over withholding investigation if PE is suspected.
Anticoagulation: Both recommend therapeutic-dose LMWH for treatment in pregnancy.
- NICE: Suggests considering switching to a VKA postpartum, with a DOAC as an alternative if not breastfeeding.
- BTS: Recommends continuing LMWH for at least 6 weeks postpartum and for a total minimum of 3 months, with VKA or DOACs as options thereafter.

Practical Clinical Flow: A Comparison

Suspected PE ->

NICE Flow: Wells Score -> If 'PE Unlikely': D-dimer -> Negative: Stop. Positive: CTPA. If 'PE Likely': Direct to CTPA.
BTS Flow: Clinical Assessment (Low/Intermediate prob): Age-adjusted D-dimer -> Negative: Stop. Positive: CTPA. (High prob): Direct to CTPA.

Confirmed PE ->

Both: Risk stratify (e.g., PESI/sPESI).
Stable Patient: Start DOAC (or LMWH/VKA).
Unstable (High-Risk): Thrombolysis (if no contraindication).
Submassive (Intermediate-High Risk): Key Difference: NICE: Anticoagulate & monitor. BTS: Consider thrombolysis if low bleeding risk.

Frequently Asked Questions (FAQs)

1. Which Wells score and D-dimer strategy should I use in my Emergency Department?

Answer: Either is valid. The NICE pathway (two-level Wells, standard D-dimer for 'unlikely' group) is simpler to implement. The BTS approach (flexible assessment, age-adjusted D-dimer for low/intermediate probability) may reduce CTPA rates in older patients. Local protocol adherence is key.

2. A patient has an unprovoked PE and wants to stop anticoagulation after 3 months. How do I decide?

Answer: Both guidelines require a shared decision-making discussion. BTS offers more specific tools, such as the HERDOO2 rule, to guide this decision, particularly for women. For men, the decision is more nuanced and based on bleeding risk.

3. How should I manage a patient with intermediate-high risk PE?

Answer: This is the most significant management difference. Follow your local protocol. NICE advises against thrombolysis. BTS permits its consideration for selected patients. Discussion with a senior clinician or specialist centre is crucial.

4. What is the first-line anticoagulant for cancer-associated PE?

Answer: Both recommend DOACs for most patients with CAT. However, both caution against their use in certain cancers (e.g., GI malignancies with active bleeding risk) and with significant drug interactions. LMWH remains a highly effective and safe alternative. The choice should be individualised.

5. Are the guidelines equally up-to-date?

Answer: NICE NG158 was updated in March 2025, making it the most recently updated document. BTS/SIGN 158 was published in 2019 and reviewed (but not updated) in 2024, confirming its content remains valid. The core recommendations of both are consistent with current international standards.

Source Links

NICE NG158 - Venous thromboembolic diseases: diagnosis, management and thrombophilia testing
NICE NG158 (Published March 2020, last updated March 2025)
BTS/SIGN 158 - British Thoracic Society Guideline for the initial outpatient management of pulmonary embolism (PE)
BTS guideline: pulmonary embolism (Published 2019, Reviewed 2024)

NICE vs BTS: Management of Pulmonary Embolism (2025)