Full blood count and blood-film interpretation in children — formative SAQs

SAQ 1 — The toddler with a low haemoglobin (10 marks, 15 minutes)

An eighteen-month-old boy is brought to the clinic with pallor noticed by his grandmother. He drinks roughly 700 millilitres of unmodified cow's milk a day and eats little else. His full blood count shows a haemoglobin of 72, a mean cell volume of 58, and a red cell distribution width that is high. The white cell count and platelet count are normal for age, and the blood film shows microcytic hypochromic red cells with no abnormal cells. [6]

a) State the most likely diagnosis and justify it from the age, the dietary history, the indices and the film. (2 marks) [5] [6]

b) Outline the iron studies you would request and interpret, and explain why a single ferritin can be misleading. (2 marks) [6]

c) Give the oral elemental iron dose, route, expected timeframe to a reticulocyte response, and the total duration of therapy. (3 marks) [5] [6]

d) Distinguish this picture from thalassaemia trait using the red cell distribution width, the red cell count and the Mentzer index, and state the confirmatory test. (3 marks) [6] [7]

SAQ 2 — The four-year-old with petechiae (10 marks, 15 minutes)

A four-year-old girl presents with a rash of petechiae over her lower limbs that appeared two days ago. She had an upper respiratory tract infection two weeks earlier. She is otherwise well and afebrile. Her full blood count shows a haemoglobin and white cell count that are normal for age, but a platelet count of 12. The blood film confirms thrombocytopenia with no blasts, no schistocytes and otherwise normal morphology. [9]

a) State the diagnosis and the two features on the history and film that exclude early leukaemia. (2 marks) [8] [9]

b) Describe how you would confirm the platelet count is genuine and not an artefact, naming the specific pre-analytical cause. (2 marks) [8]

c) Outline the principles of management, distinguishing observation from treatment, with reference to the American Society of Hematology 2019 guidance. (3 marks) [9]

d) Give the written safety-net advice you would provide before discharge, including the features that demand immediate return. (3 marks) [9] [10]