FFinalistSouthampton · 2027
Haematology
AKT · Haematology/Anaemia & red cell

Anaemia — the approach

Reduced haemoglobin — classified by MCV (micro/normo/macrocytic) to find the cause

Overview

A reduced haemoglobin concentration, not a diagnosis in itself — the task is to find the cause, and the MEAN CELL VOLUME (MCV) is the organising principle. Microcytic (iron deficiency, thalassaemia, sideroblastic), normocytic (acute blood loss, chronic disease, haemolysis, renal, marrow failure) and macrocytic (B12/folate = megaloblastic; alcohol, hypothyroid, liver, myelodysplasia = non-megaloblastic). The blood film and reticulocyte count refine it.

Recognise

  • Symptoms of anaemia: fatigue, breathlessness, pallor (conjunctival/palmar), palpitations; angina/heart failure if severe or rapid
  • MCV-based: MICROCYTIC (100) — B12/folate (megaloblastic), alcohol/liver/hypothyroid/myelodysplasia
  • Reticulocytes: HIGH (haemolysis or recent blood loss — marrow responding) vs LOW (production failure); blood film gives the diagnosis in many

Red flags

  • Iron-deficiency anaemia in an adult (especially post-menopausal women / any man) → investigate for GI malignancy (urgent referral)
  • Pancytopenia, blasts on film, or rapid/symptomatic severe anaemia → urgent haematology

Differentials & how to tell them apart

Iron-deficiency anaemiamicrocytic, low ferritin — find the bleeding source (GI/menstrual); see its card
Anaemia of chronic diseasenormocytic (or mildly microcytic), normal/high ferritin, raised inflammatory markers
B12/folate deficiencymacrocytic megaloblastic, hypersegmented neutrophils; B12 → neurology (SACD)
Haemolytic anaemiahigh reticulocytes, raised LDH/bilirubin, low haptoglobin, +/- positive DAT

Investigations

FBC with MCV, blood FILM, reticulocyte count; then cause-directed — iron studies (ferritin), B12/folate, U&Es, LFTs, TFTs, haemolysis screen (LDH, bilirubin, haptoglobin, DAT), haemoglobinopathy screen; endoscopy/coeliac for iron deficiency; bone marrow if marrow failure/malignancy suspected.

Management

Classify by MCV + reticulocytes → treat the specific cause; transfuse only if symptomatic/severe

  1. 1Anaemia is a finding, not a diagnosis — classify by MCV (micro/normo/macrocytic) with a blood film and reticulocyte count, then send cause-directed tests (ferritin, B12/folate, haemolysis screen).Gate: Iron-deficiency anaemia in any man or a post-menopausal woman → investigate for GI malignancy; replace B12 BEFORE folate to avoid precipitating subacute combined degeneration.
  2. 2Treat the specific cause; transfuse only for symptomatic or severe anaemia at a restrictive threshold; refer marrow-failure/malignant causes to haematology.
Treat the cause, not just the number — the MCV + ferritin/B12/folate/reticulocytes direct specific treatment
Iron / B12 / folate replacement as indicated — replace B12 BEFORE folate (folate alone can precipitate subacute combined degeneration)
Transfuse only for symptomatic/severe anaemia — restrictive threshold (~70 g/L, or ~80 if cardiac disease); transfusion treats the Hb, not the cause
Specialist treatment of marrow/malignant causes — haematology for myelodysplasia, marrow failure, malignancy

Key points

Anaemia → classify by MCV: micro (iron def/thalassaemia), normo (bleeding/chronic disease/haemolysis/renal), macro (B12/folate-megaloblastic vs alcohol/liver/thyroid/myelodysplasia). Reticulocytes high = haemolysis/bleeding, low = production failure. Iron deficiency in a man/post-menopausal woman → GI cancer work-up. B12 before folate.

Monitor & prognosis

Hb/MCV response to treatment, reticulocyte rise, the underlying cause.

Excellent when the cause is found and treated; depends entirely on that cause.

Source: NICE CKS (anaemia); BSH