Full Blood Count

Also written as FBC.

Investigations: chest X-ray (consolidation); full blood count and CRP; blood cultures and sputum for Gram stain, culture and GeneXpert or AFB; urea and electrolytes; pulse oximetry or arterial blood gas; HIV test; pleural fluid analysis if there is an effusion.

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Study material on Full Blood Count

Practice questions on Full Blood Count

A 62-year-old man presents with fatigue, fever and bruising. His full blood count shows WCC 40×10⁹/L with 25% circulating blasts, Hb 90 g/L and platelets 50×10⁹/L. Which investigation is required to definitively diagnose acute myeloid leukaemia?

Answer: A. Although the peripheral smear already shows circulating blasts, definitive diagnosis and subclassification of AML require bone marrow examination — combining morphology, cytochemistry, immunophenotyping, and cytogenetic/molecular analysis. ---

A 62-year-old man presents with fatigue, fever and bruising. His full blood count shows WCC 40 × 10⁹/L with 25% circulating blasts, Hb 90 g/L and platelets 50 × 10⁹/L. Which investigation is required to definitively diagnose acute myeloid leukaemia?

Answer: A. Marrow examination with immunophenotyping and cytogenetics is required for definitive diagnosis and classification of AML. ---

A 55-year-old man presents with fatigue, weight loss and splenomegaly. His full blood count shows WCC 140 × 10⁹/L with marked neutrophilia, left shift and basophilia. Which investigation is required to confirm the diagnosis of chronic myeloid leukaemia?

Answer: B. Marrow examination with cytogenetics confirms the Philadelphia chromosome, establishing the definitive CML diagnosis alongside molecular BCR-ABL testing. ---

A 62-year-old man presents with fatigue, fever and bruising. His full blood count shows WCC 40 × 10⁹/L with 25% circulating blasts, Hb 90 g/L and platelets 50 × 10⁹/L. Which investigation is required to definitively diagnose acute myeloid leukaemia?

Answer: B. While a peripheral blood smear can show blasts, a definitive diagnosis of Acute Myeloid Leukemia (AML) requires a bone marrow biopsy. Cytochemical stains (like MPO) and immunophenotyping are essential to confirm the myeloid lineage of the blasts and classify the AML subtype.

A 62-year-old man presents with fatigue, fever and bruising. His full blood count shows WCC 40 × 10⁹/L with 25% circulating blasts, Hb 90 g/L and platelets 50 × 10⁹/L. Which investigation is required to definitively diagnose acute myeloid leukaemia?

Answer: B. While a peripheral blood smear shows blasts, a definitive diagnosis of acute myeloid leukemia (AML) requires examination of the bone marrow, including cytochemical stains (e.g., MPO) and immunophenotyping to confirm the myeloid lineage of the blasts and assess the percentage.

A 62-year-old man presents with fatigue, fever and bruising. His full blood count shows WCC 40 × 10⁹/L with 25% circulating blasts, Hb 90 g/L and platelets 50 × 10⁹/L. Which investigation is required to definitively diagnose acute myeloid leukaemia?

Answer: B. While peripheral blood smear review and flow cytometry are important, a bone marrow biopsy and aspirate are essential for the definitive diagnosis of acute myeloid leukemia (AML). Cytochemical stains (like myeloperoxidase or Sudan Black B) help confirm the myeloid lineage of the blasts.

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