Laboratory medicine in primary care: Investigating iron status in microcytic anaemia
Microcytic anaemia is often assumed to indicate iron deficiency, but up to 20-30% of patients will have another diagnosis. Measurement of serum ferritin offers the best means of confirming iron deficiency, say Michael J Galloway and W Stuart A Smellie
The investigation of possible iron deficiency has changed in recent years. Traditionally, measurements of iron and iron binding capacity were performed by laboratories, but serum ferritin has now become established as a more reliable test for iron deficiency, although results in both situations can be influenced by the presence of acute or chronic inflammation.
In populations in which the prevalence of haemoglobinopathy genes is low, the finding of a microcytic anaemia is considered by some to be sufficient to indicate iron deficiency anaemia. However, this can lead to an erroneous diagnosis, as shown in the cases below.
A 69 year old man was referred for investigation of iron deficiency anaemia. History revealed that he had been feeling generally tired for two months and had lost 6 kg in weight. His haemoglobin concentration had not increased despite taking ferrous sulphate 200 mg thrice daily for eight weeks. Full blood count taken