Hematology and Oncology
Expect the anaemia algorithm, oncologic emergencies, and coagulopathy - questions that combine laboratory interpretation with a single urgent action.
Approach to anaemia
Start with MCV and the reticulocyte index. A low corrected count (<2%) means hypoproliferative disease: check iron studies (ferritin <30 ng/mL indicates deficiency; with inflammation, ferritin <100 plus transferrin saturation <20%), B12/folate, TSH, and creatinine. A high count means loss or haemolysis: LDH, haptoglobin, indirect bilirubin, direct Coombs. Iron deficiency in a man or postmenopausal woman requires gastrointestinal evaluation.
Oncologic emergencies
- Febrile neutropenia: ANC <500 with fever ≥38.3°C once or ≥38.0°C sustained. Culture, then antipseudomonal beta-lactam (cefepime or piperacillin-tazobactam) within 60 min.
- Tumour lysis: hyperkalaemia, hyperphosphataemia, hyperuricaemia, hypocalcaemia. Vigorous hydration plus allopurinol or rasburicase.
- Cord compression: dexamethasone immediately and urgent MRI of the whole spine.
Coagulopathy
DIC shows prolonged PT/aPTT, low fibrinogen, high D-dimer, and thrombocytopenia; treat the underlying cause. Heparin-induced thrombocytopenia is scored with the 4Ts; stop heparin, start a non-heparin anticoagulant, and never give platelets or start warfarin alone.
Worked example
A patient has Hb 7.5 g/dL and haematocrit 22%, with a reticulocyte count of 1.5%. The corrected count is 1.5 × (22/45) = 0.73%, an inadequate marrow response. This is hypoproliferative anaemia, so order iron studies before transfusion thresholds or haemolysis work-up. Reasoning: the reticulocyte index separates production failure from loss in one step.
Traps that cost marks
- Giving platelets in TTP or HIT.
- Calling microcytosis thalassaemia trait without excluding iron deficiency.
- Delaying antibiotics in febrile neutropenia while awaiting cultures.