Anaemia: Assessment ✅

🩸 Anaemia is a reduction in haemoglobin concentration below the normal range for age/sex/pregnancy status. It is a sign, not a diagnosis, so the important clinical task is to identify the underlying cause. A structured approach using MCV, the blood film, reticulocyte response, and targeted tests usually narrows the differential quickly.

🔍 Definition

• Adult men: Hb < 130 g/L (13 g/dL)
• Adult non-pregnant women: Hb < 120 g/L (12 g/dL)
• Pregnancy: anaemia is usually defined as Hb < 110 g/L (11 g/dL)

📖 About

• Anaemia causes reduced oxygen-carrying capacity of blood.
• Symptoms depend on severity, speed of onset, age, and cardiorespiratory reserve.
• Rapid blood loss may cause severe symptoms despite only modest early changes in Hb.
• Chronic anaemia may be surprisingly well tolerated until Hb is quite low.

📊 Causes by MCV

• Microcytic (MCV < 80 fL): iron deficiency anaemia, thalassaemia, anaemia of chronic inflammation/disease, sideroblastic anaemia, lead toxicity.
• Normocytic (MCV 80–100 fL): acute blood loss, haemolysis, CKD, anaemia of chronic disease, marrow infiltration, endocrine disease, mixed deficiency states.
• Macrocytic (MCV > 100 fL): B12 deficiency, folate deficiency, alcohol excess, liver disease, hypothyroidism, reticulocytosis, myelodysplastic syndromes, drug effects.

📑 Classification of Anaemia

🩺 Clinical features

• Fatigue, lethargy, reduced exercise tolerance
• Pallor
• Exertional dyspnoea
• Palpitations
• Dizziness or presyncope
• Angina, syncope, or heart failure if severe or in people with cardiovascular disease
• Iron deficiency clues: pica, restless legs, glossitis, angular cheilitis, koilonychia
• B12 deficiency clues: peripheral neuropathy, gait disturbance, cognitive change, glossitis
• Haemolysis clues: jaundice, dark urine, splenomegaly

🧠 Initial clinical approach

• Confirm that anaemia is real and assess severity.
• Check whether it is isolated or associated with abnormal white cells or platelets.
• Use MCV as the first sorting tool, but do not stop there.
• Look at the reticulocyte count: low response suggests underproduction; high response suggests blood loss or haemolysis.
• Always ask about bleeding, GI symptoms, diet, alcohol, drugs, chronic disease, family history, and pregnancy status where relevant.

🧪 Core investigations

• FBC and blood film: Hb, MCV, MCH, RDW, platelet count, WCC, morphology
• Reticulocyte count
• Ferritin and iron studies
• Vitamin B12 and folate
• U&E / creatinine for CKD
• LFTs and TFTs if indicated
• CRP/ESR if inflammation/chronic disease suspected
• Haemolysis screen: bilirubin, LDH, haptoglobin, DAT if haemolysis suspected
• Coeliac serology in iron deficiency anaemia
• Hb electrophoresis if thalassaemia or haemoglobinopathy suspected

🔎 Iron deficiency anaemia (IDA)

• Ferritin is the most useful initial test; a low ferritin confirms iron deficiency.
• Ferritin is an acute-phase reactant, so a “normal” ferritin does not exclude iron deficiency if inflammation is present.
• In adults, especially men and postmenopausal women, always look for a cause of blood loss — particularly gastrointestinal loss.
• Screen all people with IDA for coeliac disease using coeliac serology.
• Consider menstrual loss, pregnancy, poor intake, malabsorption, NSAID use, and GI malignancy where appropriate.

🔎 Vitamin B12 and folate deficiency

• Vitamin B12 deficiency may be caused by pernicious anaemia, gastric surgery, ileal disease, metformin, vegan diet, or malabsorption.
• Folate deficiency may be caused by poor diet, alcohol excess, malabsorption, pregnancy, haemolysis, or drug therapy.
• Do not start folic acid alone until B12 deficiency has been excluded, because neurological injury from B12 deficiency may worsen or be masked.
• Check for intrinsic factor antibodies if pernicious anaemia is suspected.

🔎 Haemolytic anaemia

• Think of haemolysis if anaemia is accompanied by reticulocytosis, jaundice, raised LDH, low haptoglobin, or splenomegaly.
• Causes include autoimmune haemolysis, hereditary spherocytosis, G6PD deficiency, sickle cell disease, microangiopathy, infection, and drugs.

🔎 Anaemia in CKD

• CKD commonly causes a normocytic, normochromic anaemia due to reduced erythropoietin production.
• Iron deficiency should be identified and treated if present.
• ESA therapy should not be started in absolute iron deficiency without also managing the iron deficiency.
• Management often requires renal guidance if anaemia is persistent or advanced CKD is present.

💊 Management

• Treat the cause, not just the Hb result.
• Iron deficiency: oral iron is first-line in many patients; IV iron may be needed if oral iron is not tolerated, ineffective, or time is short before surgery.
• B12 deficiency: treat confirmed deficiency with hydroxocobalamin; lifelong treatment is needed in pernicious anaemia and many irreversible causes.
• Folate deficiency: oral folic acid after excluding or treating B12 deficiency.
• Thalassaemia trait: usually needs explanation and family counselling rather than iron, unless iron deficiency coexists.
• CKD: iron replacement and, if appropriate, erythropoiesis-stimulating agents under CKD guidance.
• Haemolysis / marrow failure / suspected malignancy: urgent specialist referral may be needed.

💉 Blood transfusion

• Transfusion is based on clinical status, not Hb alone.
• Consider urgency, symptoms, active bleeding, cardiovascular disease, and speed of onset.
• Severe symptomatic anaemia, haemodynamic compromise, or acute coronary symptoms need urgent assessment.

🚨 Red flags

• Pancytopenia or bicytopenia
• Suspected haemolysis
• Rapidly falling Hb
• Weight loss, night sweats, lymphadenopathy, hepatosplenomegaly
• Neurological features of B12 deficiency
• IDA in an adult man or postmenopausal woman without obvious explanation
• Severe anaemia with chest pain, syncope, heart failure, or haemodynamic instability

📚 References

• NICE CKS – Anaemia: iron deficiency
• NICE CKS – Iron deficiency anaemia: investigations
• NICE CKS – Iron deficiency anaemia: management
• NICE CKS – Anaemia: B12 and folate deficiency
• NICE CKS – B12 and folate deficiency: management
• BNF (NICE) – Hydroxocobalamin
• NICE NG203 – Chronic kidney disease: assessment and management

💡 Clinical pearl:
Start with MCV + reticulocytes + ferritin + film.
Microcytic often means iron deficiency or thalassaemia.
Macrocytic means B12/folate, alcohol, liver, thyroid, marrow, or drugs.
Normocytic means think blood loss, haemolysis, CKD, chronic disease, or marrow pathology.
Always ask: Where is the blood loss? Is there haemolysis? Is the marrow responding?