Discuss the classification of anaemia and the diagnostic approach to a patient with anaemia.

Definition

Anaemia is a reduction in haemoglobin concentration below the normal range for age, sex and physiological state, resulting in reduced oxygen-carrying capacity. WHO thresholds: below 13 g/dL in adult men, 12 g/dL in non-pregnant women, and 11 g/dL in pregnancy. India carries one of the highest anaemia burdens in the world, with iron deficiency and nutritional causes predominating, compounded by hookworm infestation, malaria and haemoglobinopathies.

Classification

A. Morphological — by mean corpuscular volume (MCV). The most useful practical starting point.

B. Pathophysiological — by mechanism. This is the classification that directs management:

1. Decreased production — nutrient deficiency (iron, B12, folate), marrow failure (aplastic anaemia), marrow infiltration (leukaemia, myeloma, metastases, myelofibrosis), chronic disease, chronic kidney disease (erythropoietin deficiency), endocrine failure.

2. Increased destruction (haemolysis) — intrinsic (membrane, enzyme, haemoglobin defects) or extrinsic (immune, microangiopathic, infection, hypersplenism).

3. Blood loss — acute (trauma, gastrointestinal, obstetric) or chronic (menorrhagia, gastrointestinal, hookworm).

Clinical Approach

History:

• Symptoms of anaemia: fatigue, exertional dyspnoea, palpitations, dizziness, headache, poor concentration; angina and heart failure in the elderly.
• Clues to cause: dietary history (vegetarian diet — B12 deficiency; poor iron intake), menstrual and obstetric history (menorrhagia is the commonest cause in Indian women of reproductive age), gastrointestinal symptoms — dyspepsia, altered bowel habit, melaena, weight loss; worm infestation; drug history (NSAIDs, aspirin, anticoagulants, antitubercular drugs, methotrexate); alcohol; family history and consanguinity (haemoglobinopathy); previous surgery (gastrectomy, ileal resection); chronic disease — renal, hepatic, rheumatological, malignancy; and jaundice or dark urine suggesting haemolysis.

Examination:

• Pallor (conjunctiva, tongue, palm, nail bed) — insensitive below moderate anaemia.
• Iron deficiency: koilonychia, angular stomatitis, glossitis, brittle hair, pica.
• B12 deficiency: lemon-yellow tinge (pallor with mild jaundice), glossitis, peripheral neuropathy and posterior column signs.
• Haemolysis: jaundice, splenomegaly, leg ulcers, gallstones, frontal bossing in thalassaemia.
• Marrow failure or infiltration: purpura, bleeding, infection, bone tenderness, lymphadenopathy, hepatosplenomegaly.
• Chronic disease: clubbing, lymph nodes, masses, features of renal or hepatic failure.
• Cardiovascular: tachycardia, flow murmur, features of heart failure in severe anaemia.
• Per rectal examination is mandatory in unexplained iron deficiency.

Investigations — a Stepwise Scheme

Step 1 — the basics that classify the anaemia:

• Complete blood count with red cell indices — MCV, MCH, MCHC, RDW (raised early in iron deficiency, normal in thalassaemia trait), and the white cell and platelet counts. Pancytopenia points to marrow failure, infiltration or hypersplenism.
• Peripheral smear — the single most informative and cheapest test. Look for hypochromia and microcytosis, target cells (thalassaemia, liver disease), macro-ovalocytes with hypersegmented neutrophils (megaloblastic), schistocytes (microangiopathy), spherocytes (hereditary spherocytosis, autoimmune haemolysis), sickle cells, basophilic stippling (lead, thalassaemia), blasts, rouleaux (myeloma), and parasites.
• Reticulocyte count — the pivotal test of marrow response:
• Low or normal → failure of production (deficiency, marrow disease, chronic disease)
• Raised → haemolysis or recent blood loss

Step 2 — directed by the MCV and reticulocyte count:

Step 3 — special tests where indicated: bone marrow aspiration and biopsy (unexplained cytopenias, suspected leukaemia, myeloma, aplasia, infiltration, or to assess iron stores directly), upper and lower gastrointestinal endoscopy, stool for occult blood and ova, coeliac serology, HIV, and imaging for malignancy.

Principles of Management

1. Find and treat the cause — never treat anaemia as a diagnosis in itself.

2. Correct the deficiency — oral iron with dietary advice, parenteral iron for intolerance or malabsorption, B12 and folate replacement.

3. Transfuse only for haemodynamic compromise, symptomatic severe anaemia, or active bleeding — not to normalise a number. Transfusion carries real risks and does not address the cause.

4. Erythropoietin for anaemia of chronic kidney disease, with adequate iron stores.

5. Public health measures in the Indian context: iron and folic acid supplementation programmes, deworming, food fortification, malaria control, and premarital and antenatal screening for haemoglobinopathies.