Hematology
Hematology questions are built from the complete blood count and the peripheral smear. Egypt's thalassaemia and sickle cell burden means haemoglobinopathy questions appear alongside the standard anaemia, bleeding and malignancy cases.
Anaemia algorithm
- Start with mean corpuscular volume and reticulocyte count. Low reticulocytes mean underproduction; high reticulocytes mean loss or destruction.
- Microcytic: iron deficiency (low ferritin, high total iron-binding capacity, low saturation), thalassaemia trait (normal ferritin, raised haemoglobin A2 on electrophoresis, target cells), anaemia of chronic disease (normal or high ferritin, low saturation).
- Macrocytic with low B12 or folate: check methylmalonic acid; look for neurological signs with B12 deficiency and treat before folate to avoid masking.
- Haemolysis: raised lactate dehydrogenase and indirect bilirubin, low haptoglobin, raised reticulocytes; direct antiglobulin test separates immune from non-immune.
Bleeding and platelets
- Isolated thrombocytopenia with a normal film and no other cytopenia suggests immune thrombocytopenia; treat with steroid when platelets are below 30 or bleeding.
- Schistocytes, anaemia, thrombocytopenia, renal failure and neurological signs indicate thrombotic thrombocytopenic purpura: urgent plasma exchange plus steroid, and avoid platelet transfusion unless life-threatening bleeding.
Malignancy and transfusion
- Chronic myeloid leukaemia: Philadelphia chromosome or BCR-ABL1; treat with a tyrosine kinase inhibitor.
- Multiple myeloma: CRAB features (hypercalcaemia, renal failure, anaemia, bone lesions) plus paraprotein; confirm with bone marrow and use the serum free light chain ratio.
- Acute myeloid leukaemia: blasts 20 percent or more with Auer rods; urgent referral for induction.
Worked example
A 26-year-old woman has fatigue, haemoglobin 7.8 g/dL, mean corpuscular volume 68 fL, ferritin 6 ng/mL, and platelets 450,000. This is iron deficiency anaemia with reactive thrombocytosis. The key step is not simply prescribing iron but explaining the deficiency: ask about menstrual loss, screen for gastrointestinal blood loss and coeliac disease, and recheck the count after three months of oral iron; failure to respond means non-adherence, continuing loss, or a wrong diagnosis.
Traps
Diagnosing thalassaemia trait as iron deficiency and giving unnecessary iron; transfusing platelets in thrombotic thrombocytopenic purpura; treating B12 deficiency with folate alone; and calling a paraprotein benign without checking the free light chain ratio and skeletal survey.