Hematology and Oncology
Expect questions on anaemia classification, iron studies in inflammation, haemolysis, oncological emergencies and anticoagulation in cancer.
Anaemia by MCV
Microcytic anaemia suggests iron deficiency, thalassaemia or anaemia of chronic disease. Ferritin below 30 ng/mL is the most useful marker of iron deficiency, but ferritin rises with inflammation; when CRP is high, use transferrin saturation below 20% instead. Macrocytic anaemia suggests B12 or folate deficiency, alcohol, hypothyroidism or myelodysplasia. Methylmalonic acid rises in B12 deficiency but not folate deficiency, which distinguishes them when both are borderline.
Haemolysis
Look for raised LDH and indirect bilirubin, low haptoglobin and reticulocytosis; a positive direct antiglobulin test points to immune haemolysis.
Oncological emergencies
- Febrile neutropenia (absolute neutrophil count below 500 with fever) needs cultures and an anti-pseudomonal beta-lactam within 60 minutes.
- Tumour lysis syndrome produces hyperkalaemia, hyperphosphataemia, hyperuricaemia and hypocalcaemia; rasburicase is contraindicated in G6PD deficiency.
- Cord compression needs dexamethasone and urgent MRI.
Cancer-associated thrombosis
Low-molecular-weight heparin or a DOAC is used; DOACs are avoided in luminal gastrointestinal or genitourinary cancers because of bleeding risk.
Worked example
A microcytic anaemia with ferritin 120 ng/mL but CRP 80 mg/L and transferrin saturation 12% still represents iron deficiency - the ferritin is falsely normal because it is an acute-phase reactant.
Traps that cost marks
- Excluding iron deficiency on a normal ferritin during inflammation.
- Transfusing on haemoglobin alone without clinical context.
- Giving rasburicase without checking G6PD.