Anaemia: diagnostic approach — formative SAQs

SAQ 1 (10)

A 20-month-old has a haemoglobin of 78 g/L with a mean corpuscular volume of 66 femtolitres, microcytic hypochromic indices, and a normal white cell and platelet count. The child drinks about 800 millilitres of cow's milk a day. ^[1]

1. State a one-sentence problem representation and justify the MCV and reticulocyte classification grid you used. (3) ^{[1] [3]}
2. Outline the directed second-line tests and how you would interpret ferritin as an acute-phase reactant. (4) ^{[1] [6]}
3. Detail cause-directed management including the oral iron dose, expected response, and how to avoid missing the microcytic mimics. (3) ^{[1] [4] [6]}

Model answer

Problem representation. Twenty-month-old with dietary risk, microcytic hypochromic anaemia, low or normal reticulocytes, and no red flags for marrow disease, consistent with iron deficiency. The grid sorts by mean corpuscular volume into micro, normo or macro, and by reticulocyte count into high (loss or destruction) versus low (production failure); this child sits in microcytic and low reticulocyte, the iron-deficiency cell. ^{[1] [3]}

Directed tests. Iron studies: ferritin, serum iron, transferrin or total iron-binding capacity, and transferrin saturation. Low ferritin with high binding capacity confirms deficiency, but ferritin is an acute-phase reactant, so a normal or high value in inflammation does not exclude iron deficiency and the soluble transferrin receptor or full iron panel helps. Add a haemoglobinopathy screen if microcytosis is disproportionate, the red cell count is high, or ancestry suggests trait. ^{[1] [6]}

Management. Reduce cow's milk to about 500 millilitres daily, improve iron-rich solids, start oral elemental iron at 3 to 6 milligrams per kilogram per day, and plan a response check. Expect a reticulocyte rise within seven to ten days then a haemoglobin climb; failure to rise means wrong diagnosis, ongoing loss, non-adherence or malabsorption, not more iron. Avoid empiric iron when thalassaemia trait, anaemia of inflammation or lead is plausible. ^{[1] [4] [6]}