How to work through any anaemia case in an exam: start with the MCV and reticulocyte count, then choose the tests that settle the cause, with case-based MCQs and the full quiz.
- Step 1: classify by MCV: microcytic, normocytic or macrocytic
- Step 2: check the reticulocyte count: high means loss or haemolysis, low means production failure
- Microcytic: iron deficiency versus thalassaemia trait versus anaemia of inflammation
- Macrocytic: megaloblastic (B12, folate) versus non-megaloblastic (alcohol, liver, hypothyroidism, MDS)
- Haemolysis: raised reticulocytes, LDH and bilirubin, low haptoglobin; DAT separates immune causes
The approach
| MCV | Common causes |
|---|---|
| Low (below 80 fL) | Iron deficiency, thalassaemia trait, anaemia of inflammation (late), sideroblastic anaemia |
| Normal (80โ100 fL) | Acute blood loss, haemolysis, anaemia of chronic disease, renal failure, marrow infiltration |
| High (above 100 fL) | B12 or folate deficiency, alcohol, liver disease, hypothyroidism, MDS, reticulocytosis, drugs such as hydroxyurea |
The reticulocyte count tells you whether the marrow is responding. A high count means loss or destruction; a low count means the marrow is not producing enough.
Microcytic anaemia
| Test | Iron deficiency | Thalassaemia trait | Anaemia of inflammation |
|---|---|---|---|
| Ferritin | Low | Normal | Normal or high |
| Serum iron and TIBC | Low iron, high TIBC | Normal | Low iron, low TIBC |
| RBC count | Low | Normal or high | Low |
| Mentzer index (MCV/RBC) | Above 13 | Below 13 | Above 13 |
| HbA2 | Normal or low | Raised in ฮฒ-thalassaemia trait | Normal |
Macrocytic anaemia
- Megaloblastic: oval macrocytes, hypersegmented neutrophils (five or more lobes) and, in severe cases, pancytopenia. Check B12, folate and anti-intrinsic factor antibodies; treat B12 before folate to avoid worsening neurological damage.
- Non-megaloblastic: round macrocytes without hypersegmentation, as in alcohol, liver disease and hypothyroidism. Consider MDS in an older patient with cytopenias.
Pathology MCQPractice questions
Three quick questions, then the full quiz.
A woman has Hb 9 g/dL, MCV 68 fL, RBC 3.6 ร 10ยนยฒ/L and ferritin 6 ยตg/L. What is the diagnosis?
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Which finding most strongly suggests megaloblastic anaemia?
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A normocytic anaemia with raised reticulocytes, raised LDH, low haptoglobin and a positive DAT suggests:
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- Start with MCV, then the reticulocyte count.
- Low ferritin confirms iron deficiency; a Mentzer index below 13 favours thalassaemia trait.
- Hypersegmented neutrophils point to megaloblastic anaemia; replace B12 before folate.
- Haemolysis plus a positive DAT means immune haemolysis.
Hoffbrand AV, Steensma DP. Hoffbrandโs Essential Haematology, 8th ed. Wiley-Blackwell; 2019 ยท Greer JP, Rodgers GM, Glader B, et al., eds. Wintrobeโs Clinical Hematology, 15th ed. Wolters Kluwer; 2023 ยท Bain BJ. Blood Cells: A Practical Guide, 6th ed. Wiley-Blackwell; 2022
High-Yield, Board-Style Image MCQs & Interactive Whole Slide Images
High-resolution virtual microscopy with questions aligned to ABP, FRCPath, NEET-SS, DM Hematopathology and MD/DNB.
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