NICE vs SIGN: Management of Parkinson’s Disease (2025)
For UK clinicians managing Parkinson's disease (PD), two national evidence-based guidelines are paramount: the National Institute for Health and Care Excellence (NG71, updated July 2017) and the Scottish Intercollegiate Guidelines Network (SIGN 113, published January 2010, with a key addendum in March 2021). While both aim to standardise and improve care, their timelines, update processes, and some recommendations differ significantly. This comparison provides a factual analysis for clinicians, highlighting key divergences and practical implications for clinical practice across the UK.
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Key Context: The NICE guideline is newer and more comprehensive. The SIGN guideline is older, but its 2021 addendum provides crucial, up-to-date recommendations on advanced therapies, making it the primary reference for this aspect of care. Clinicians should view these documents as complementary.
Diagnosis and Assessment
NICE (NG71, 2017)
- Referral: Recommends rapid referral to a specialist (neurologist or geriatrician) for any patient with suspected PD, without using a specific symptom checklist.
- Diagnostic Criteria: Emphasises diagnosis based on the UK Parkinson's Disease Society Brain Bank clinical diagnostic criteria.
- Imaging: Advises considering SPECT (DaTSCAN) if there is diagnostic uncertainty, particularly to differentiate from essential tremor, drug-induced parkinsonism, or vascular parkinsonism. It is not recommended for routine diagnosis.
- Monitoring: Stresses the use of validated scales for holistic assessment, specifically recommending the Unified Parkinson's Disease Rating Scale (UPDRS) or the Hoehn and Yahr scale for disease staging.
SIGN (113, 2010)
- Referral & Diagnosis: Also supports referral to a specialist and diagnosis based on the UK Brain Bank criteria. The core 2010 document aligns closely with NICE on basic diagnostic principles.
- Key Difference in Age of Guidance: As the SIGN guideline predates NICE, it does not reflect the same level of detail or more recent consensus on the role of DaTSCAN and monitoring scales, which are more explicitly detailed in NG71.
Practical Takeaway: For initial diagnosis and assessment, NICE NG71 provides the more current and detailed framework. The recommendation for rapid specialist referral is consistent across both guidelines and should be considered a standard of care.
Pharmacological Treatment: Initial and Advanced
Initial Pharmacotherapy
NICE (NG71, 2017): Adopts a patient-choice-centred, non-levodopa-sparing approach. It recommends that the choice of initial therapy (levodopa, dopamine agonists, or MAO-B inhibitors) should be made jointly by the clinician and patient after discussion of the advantages and disadvantages of each drug class. Age and comorbidity are important factors in this decision, but there is no strict age cut-off for levodopa initiation.
SIGN (113, 2010): Reflects the older, levodopa-sparing paradigm. It suggests that dopamine agonists or MAO-B inhibitors may be considered as initial monotherapy, particularly in younger patients (younger than 65–70 years), to delay the onset of motor complications associated with levodopa.
Key Difference: This is a major philosophical divergence. NICE's approach is more pragmatic and less restrictive, while SIGN's 2010 guidance is more cautious about early levodopa use.
Advanced Therapies (Motor Fluctuations & Dyskinesia)
This is the area of greatest divergence due to the SIGN 2021 Addendum.
SIGN (2021 Addendum): This is the definitive UK guidance for advanced therapies. It provides specific, graded recommendations:
- Levodopa-carbidopa intestinal gel (LCIG): Recommended as an option for patients with advanced PD with severe motor fluctuations and dyskinesia inadequately controlled by optimised oral therapy.
- Apomorphine infusion: Recommended as an option.
- Deep brain stimulation (DBS): Recommended as an option for patients with advanced PD who are levodopa-responsive and have no significant comorbidities, especially those with early motor complications.
NICE (2017): NG71 covers these therapies but in less specific terms. It states that DBS, apomorphine, and Duodopa® (LCIG) "can be considered" for people with advanced PD. Crucially, NICE has separate, detailed Technology Appraisals for these treatments (e.g., TA679 for LCIG), which provide the funding mandate for England and Wales. The 2017 guideline itself lacks the specificity of the SIGN addendum.
Practical Takeaway: For initial treatment, follow NICE NG71. For evaluating and recommending advanced therapies, the SIGN 2021 Addendum is the primary clinical reference, but clinicians must be aware of the relevant NICE Technology Appraisals for commissioning and funding purposes.
Special Situations
Non-Motor Symptoms & Psychosis
NICE (2017) offers more comprehensive guidance on a wider range of non-motor symptoms, including sleep disorders, orthostatic hypotension, and impulse control disorders.
Psychosis: Both guidelines caution against typical antipsychotics. NICE specifically recommends clozapine (with mandatory blood monitoring) for treating psychosis in PD. SIGN 2010 mentions clozapine and quetiapine but notes the evidence for quetiapine is less robust. The newer NICE guidance is more definitive.
Palliative Care
NICE includes a strong section on palliative care principles, emphasising the need for advance care planning, management of end-of-life symptoms, and continuing dopaminergic therapy to avoid a pallid state. SIGN 2010 does not cover this area in depth.
Practical Takeaway: For management of non-motor symptoms, palliative care, and holistic patient support, NICE NG71 is the more detailed and contemporary resource.
Practical Clinical Flow for UK Clinicians
- Suspicion of PD in Primary Care: Action is consistent. Make a rapid referral to a neurologist or geriatrician with a specialist interest in PD.
- Diagnosis & Baseline Assessment: Follow NICE NG71. Use UK Brain Bank criteria. Consider DaTSCAN for diagnostic uncertainty. Establish a baseline using UPDRS.
- Initial Treatment Discussion: Follow NICE NG71. Have a detailed conversation with the patient about levodopa, dopamine agonists, and MAO-B inhibitors, tailoring the choice to the individual. Do not automatically withhold levodopa in younger patients.
- Management of Motor Complications:
- First, optimise oral therapy (adjust levodopa timing/dose, add COMT/MAO-B inhibitors, etc.).
- When oral optimisation is insufficient, refer for assessment for advanced therapies. Use the SIGN 2021 Addendum as the clinical rationale for considering LCIG, apomorphine, or DBS.
- Holistic & Non-Motor Management: Use NICE NG71 for guidance on psychosis (clozapine), sleep disorders, orthostatic hypotension, and integrating palliative care principles early.
- Multidisciplinary Team (MDT): Both guidelines strongly advocate for MDT care involving Parkinson's nurses, physiotherapists, occupational therapists, and speech and language therapists.
Frequently Asked Questions (FAQs)
1. Which guideline should I primarily use in my daily practice?
Use NICE NG71 (2017) as your core guideline for diagnosis, initial treatment, and non-motor symptom management. However, for the specific assessment and recommendation of advanced therapies (LCIG, apomorphine, DBS), the SIGN 2021 Addendum is essential and more current. They are complementary.
2. A 60-year-old patient is newly diagnosed. Should I start levodopa or a dopamine agonist?
According to NICE NG71, the decision should be personalised. Discuss the pros and cons of both options with the patient. Levodopa is more effective for motor symptoms but carries a higher risk of dyskinesias long-term. Dopamine agonists are less effective for motor symptoms but have a lower risk of dyskinesias, though a higher risk of non-motor side effects (e.g., impulse control disorders). NICE does not prohibit levodopa as first-line in a 60-year-old.
3. What is the most evidence-based advanced therapy for a patient with severe "on-off" fluctuations?
The SIGN 2021 Addendum does not rank one therapy above another. The choice between LCIG, apomorphine, and DBS depends on patient-specific factors: phenotype, presence of non-motor symptoms, cognitive status, and patient preference. A specialist MDT assessment is crucial to determine the most suitable option.
4. Which antipsychotic is recommended for psychosis in PD?
NICE NG71 definitively recommends clozapine (with mandatory haematological monitoring). Other atypical antipsychotics like quetiapine may be used in practice, but the evidence base from the guidelines is strongest for clozapine. Typical antipsychotics (e.g., haloperidol) are contraindicated.
5. How does the funding process work for advanced therapies in England/Wales vs. Scotland?
The clinical recommendation (based on SIGN 2021) is UK-wide. However, the funding mandate comes from different sources:
- England & Wales: NICE Technology Appraisals (e.g., TA679 for LCIG) legally require NHS funding for treatments that are recommended.
- Scotland: The Scottish Medicines Consortium (SMC) issues similar advice, often informed by SIGN guidance.
Source Links
- NICE Guideline NG71 (July 2017): Parkinson’s disease in adults
- SIGN Guideline 113 (Jan 2010): Diagnosis and pharmacological management of Parkinson’s disease
- SIGN Addendum (March 2021): Addendum to SIGN 113: Advanced therapies for Parkinson's disease
- NICE Technology Appraisal TA679 (Jan 2021): Levodopa-carbidopa intestinal gel for advanced Parkinson's disease