Define anaemia. Classify anaemia morphologically and aetiologically. Describe the approach to its investigation.

Definition

• Anaemia is a sign, never a diagnosis — the cause must always be established
• India has one of the highest burdens in the world, with over half of women and young children affected, most of it iron deficiency
• Haemoglobin may be falsely normal in dehydration and falsely low in pregnancy from plasma expansion

Morphological Classification

• The MCV is the single most useful first step in classifying anaemia, and is available on every automated blood count
• A raised RDW (red cell distribution width) indicates anisocytosis and is characteristically high in iron deficiency but normal in thalassaemia trait — a cheap and useful discriminator

Aetiological Classification

Clinical Features

• General — fatigue, weakness, dyspnoea on exertion, palpitations, dizziness, headache
• Pallor — best assessed in the conjunctiva, tongue, palm and nail beds
• Cardiovascular — tachycardia, wide pulse pressure, a haemic systolic murmur; in severe cases high-output cardiac failure
• Symptoms depend on the rate of onset as much as the level — a slowly developing haemoglobin of 6 g/dL may be tolerated remarkably well, while a rapid fall to 9 causes collapse
• Specific pointers — koilonychia and angular stomatitis (iron), glossitis and neurological signs (B12), jaundice and splenomegaly (haemolysis), bone changes (thalassaemia), bleeding and infection (aplastic)

Investigation

• 1. Full blood count with indices and RDW → 2.
• Peripheral smear — cheap, rapid and often diagnostic on its own → 3.
• Reticulocyte count — production versus destruction → 4.
• Directed tests — iron studies, B12 and folate, haemolytic screen (LDH, bilirubin, haptoglobin, Coombs), haemoglobin electrophoresis → 5.
• Bone marrow examination where the cause remains unclear, or if aplasia, leukaemia or infiltration is suspected → 6.
• Search for the underlying disease — endoscopy, stool for occult blood and ova

Physiological Adaptations to Anaemia

• These adaptations explain why a slowly developing anaemia is so well tolerated — a patient may walk into clinic with a haemoglobin of 4 g/dL and few symptoms, which is common in India
• They also explain the danger of rapid transfusion in chronic anaemia: the plasma volume is already expanded, and overload precipitates pulmonary oedema

Applied Aspects

• Never treat anaemia blindly with iron — investigate first. Iron given in thalassaemia trait causes iron overload without benefit, and iron given in undiagnosed colonic carcinoma delays the diagnosis
• In an Indian adult, iron deficiency plus hookworm should always be considered, and stool examination is cheap; deworming is part of treatment
• Iron deficiency anaemia in a man or a postmenopausal woman means gastrointestinal blood loss until proved otherwise, and requires endoscopy
• The peripheral smear is the most under-used investigation — it costs almost nothing and may show sickle cells, malarial parasites, hypersegmented neutrophils or blasts
• Transfusion is for symptoms, not for a number; in chronic anaemia the underlying cause should be treated and transfusion avoided where possible
• Anaemia in pregnancy increases maternal mortality, preterm birth and low birth weight, and is a major preventable contributor to poor outcomes in India
• A dimorphic smear — two distinct populations of red cells — indicates either a mixed deficiency or a recently transfused patient, and the MCV may be misleadingly normal
• Pancytopenia demands a marrow examination, since the differential includes aplastic anaemia, leukaemia, myelodysplasia, megaloblastic anaemia, hypersplenism and kala-azar
• The National Anaemia Mukt Bharat programme targets six beneficiary groups with supplementation, deworming and fortification — the scale of the problem justifies a population approach rather than case-by-case treatment
• Correcting anaemia improves work capacity and school performance measurably, so the case for treating it is economic as well as clinical
• Haemoglobin should be checked by an accurate method — the cyanmethaemoglobin method or an automated counter; colour-scale and copper-sulphate methods used in field settings are screening tools only
• Anaemia in the elderly is never "just age", and about a fifth have an occult malignancy or myelodysplasia when properly investigated
• Repeat the count before acting on a single abnormal result, since dilution, posture and sampling technique all shift the haemoglobin measurably
• Anaemia is a sign of an underlying disorder, and the disorder is what kills — the discipline of always asking why is what separates good practice from reflexive prescribing