Compare Investigation thresholds for Anaemia across NICE, BSH, and SIGN. Built for Adults. Setting: Primary & Secondary. Urgency: Routine.
Clear thresholds help clinicians answer "when do I act?" for anaemia, aligning expectations between NICE, BSH, and SIGN. Use this side-by-side view to decide when to refer, escalate, monitor, or initiate treatment.
Anaemia affects approximately 1 in 7 adults in the UK, with prevalence increasing to over 25% in those aged 85 and older. The condition represents a significant clinical burden across primary and secondary care settings, often serving as an important marker of underlying pathology. The key challenge in anaemia management lies in distinguishing between self-limiting nutritional deficiencies and more serious underlying conditions like malignancy, chronic kidney disease, or gastrointestinal bleeding.
Getting investigation thresholds right is critical because delayed diagnosis can lead to unnecessary morbidity, while over-investigation strains healthcare resources and increases patient anxiety. NICE takes a pragmatic, evidence-based approach focused on cost-effectiveness across the NHS. BSH provides specialist haematology perspectives with detailed laboratory interpretation. SIGN emphasizes Scottish population considerations and practical primary care applications. Understanding these philosophical differences helps clinicians apply the most appropriate guidance for their specific patient population and clinical setting.
| Guideline body | Primary focus | Typical setting | Publication/update |
|---|---|---|---|
| NICE | Broad NHS implementation, cost-effectiveness | Primary & Secondary care | 2024 (NG231) |
| BSH | Specialist haematology, laboratory interpretation | Secondary care, haematology clinics | 2023 (Update) |
| SIGN | Scottish population, primary care practicalities | Primary care, Scottish health boards | 2025 (SIGN 164) |
NICE serves as the default reference for most English and Welsh practices, while BSH provides essential specialist input for complex cases. SIGN offers specific Scottish population considerations and practical primary care workflow integration. Cross-reference between guidelines when managing patients with atypical presentations, significant comorbidities, or when local policy mandates specific approaches.
| Threshold parameter | NICE | BSH | SIGN | Notes |
|---|---|---|---|---|
| Haemoglobin (g/L) - Men | <130 | <130 | <130 | All bodies align for adult males |
| Haemoglobin (g/L) - Women | <120 | <120 | <120 | Consensus for non-pregnant women |
| MCV (fL) - Microcytic | <80 | <80 | <80 | Threshold for iron deficiency workup |
| MCV (fL) - Macrocytic | >100 | >100 | >100 | BSH adds: >115 requires urgent B12/folate |
| Ferritin (μg/L) | <30 | <30 (inflammatory states: <100) | <30 | BSH provides inflammation adjustment |
| Absolute reticulocyte count | Not specified | <50×10⁹/L suggests inadequate response | Not specified | BSH specialist parameter |
NICE recommends repeating full blood count within 2-4 weeks for borderline anaemia (Hb 110-119 g/L women, 120-129 g/L men) to confirm persistence. For established anaemia, initiate basic investigations (ferritin, B12, folate, renal function) immediately. Monitor treatment response at 4-week intervals for iron deficiency, 8-12 weeks for B12/folate replacement. Escalate frequency if Hb drops >20 g/L within 4 weeks or patient develops symptoms.
BSH emphasizes comprehensive initial testing including haematinics, blood film, and inflammatory markers. For unexplained anaemia, recommend specialist referral within 4 weeks. Monitoring intervals are more intensive: weekly for severe anaemia (Hb <80 g/L), fortnightly for moderate cases. BSH specifically highlights the importance of reticulocyte response monitoring within 7-10 days of initiating treatment.
SIGN focuses on practical primary care application with emphasis on patient symptoms alongside numerical thresholds. Recommend repeat testing within 1-2 weeks if symptomatic regardless of Hb level. For asymptomatic mild anaemia, repeat at 3 months. SIGN provides specific Scottish population considerations including higher threshold for investigation in elderly (>65 years) with multiple comorbidities.
| Trigger scenario | NICE recommendation | BSH recommendation | SIGN recommendation |
|---|---|---|---|
| Hb <80 g/L | Urgent secondary care referral (within 2 weeks) | Immediate haematology assessment | Urgent referral (within 1 week) |
| Rapid drop (>20 g/L in 4 weeks) | Expedited referral (within 4 weeks) | Urgent investigation for blood loss/haemolysis | Expedited referral (within 2 weeks) |
| Unexplained anaemia after basic workup | Routine haematology referral (within 6 weeks) | Specialist assessment within 4 weeks | Consider referral if persistent >3 months |
| Macrocytic anaemia with neurological symptoms | Urgent neurology/haematology referral | Immediate B12 treatment and specialist input | Urgent secondary care assessment |
| Anaemia of chronic disease not responding | Consider specialist input after 3 months | Haematology assessment for ESA consideration | Shared care with secondary care |
| Pregnant women Hb <105 g/L | Obstetric haematology referral | Joint obstetric-haematology management | Obstetric-led management with haematology input |
Presentation: 78-year-old woman with osteoarthritis, Hb 115 g/L, MCV 82 fL, asymptomatic.
Analysis: NICE would recommend repeat FBC in 2-4 weeks. BSH would recommend immediate ferritin, B12, folate, and renal function. SIGN would consider comorbidity impact and may accept monitoring if asymptomatic. Most appropriate approach: basic investigations (ferritin, renal function) given age, with repeat FBC if normal.
Action: Check ferritin, B12, folate, U&Es. If normal, repeat FBC in 1 month.
Presentation: 45-year-old man with fatigue, shortness of breath, Hb 88 g/L, MCV 112 fL.
Analysis: All bodies agree on urgent referral. NICE recommends within 2 weeks, BSH immediate assessment, SIGN within 1 week. BSH would emphasize immediate B12/folate testing while arranging referral.
Action: Urgent haematology referral (within 1 week), check B12/folate immediately, consider treatment if deficient.Presentation: 35-year-old woman with iron deficiency anaemia, 3 months oral iron, Hb improved from 95 to 105 g/L but plateaued.
Analysis: NICE would consider referral after 3 months non-response. BSH would recommend earlier specialist assessment for malabsorption/bleeding investigation. SIGN would emphasize gastrointestinal symptoms assessment.
Action: Refer to gastroenterology for malabsorption/bleeding workup, consider intravenous iron.
While no formal risk prediction tool exists specifically for anaemia investigation thresholds, clinicians should consider several clinical decision factors:
Comorbidity burden: Patients with cardiovascular disease, CKD, or respiratory conditions tolerate anaemia poorly - lower threshold for investigation and intervention.
Age-adjusted considerations: Elderly patients may have higher baseline creatinine masking renal impairment contribution - consider eGFR calculation.
Symptom severity score: Use functional assessment (ability to climb stairs, daily activities) alongside numerical thresholds.
Blood loss risk factors: NSAID use, anticoagulation, family history of GI malignancy lower threshold for endoscopic investigation.
| Guideline body | Position | Population & urgency |
|---|---|---|
| NICE | Position on Investigation thresholds for Anaemia | Adults | Urgency: Routine | Setting: Primary & Secondary |
| BSH | Position on Investigation thresholds for Anaemia | Adults | Urgency: Routine | Setting: Primary & Secondary |
| SIGN | Position on Investigation thresholds for Anaemia | Adults | Urgency: Routine | Setting: Primary & Secondary |
Refer to the full guidelines for exact wording and local adaptations. This summary is for rapid orientation and multidisciplinary alignment.
Full guideline references:
This comparison is intended for clinical decision support and education. Always refer to the full published guidelines for definitive recommendations and the most up-to-date evidence. Clinical decisions should be individualized based on patient context and preferences.