Practice Cases in primary care laboratory medicine

Investigating iron status in microcytic anaemia

BMJ 2006; 333 doi: https://doi.org/10.1136/bmj.38979.358032.BE (Published 12 October 2006) Cite this as: BMJ 2006;333:791
  1. Michael J Galloway ([email protected]), haematologist1,
  2. W Stuart A Smellie, chemical pathologist2
  1. 1 City Hospitals Sunderland NHS Foundation Trust, Sunderland Royal Hospital, Sunderland SR4 7TP,
  2. 2Clinical Laboratory, General Hospital, Bishop Auckland DL14 6AD
  1. Correspondence to: M J Galloway
  • Accepted 13 September 2006

Microcytic anaemia is often assumed to indicate iron deficiency, but up to 20-30% of patients will have another diagnosis, particularly anaemia of chronic inflammation or myelodysplasia. Measurement of serum ferritin offers the best means of confirming iron deficiency, although in some cases a trial of iron may be required.

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.

Case 1

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 in primary care had shown haemoglobin 95 g/l, mean cell volume 73 fl, white cell count 7.5×109/l, and platelets 480×109/l. Subsequent investigations in secondary care also showed an erythrocyte sedimentation rate of 80 mm in first hour and a ferritin concentration of 577 µg/l, and these high values indicated that the diagnosis was anaemia of chronic inflammation (chronic disease). Subsequent computed tomography revealed the presence of a renal carcinoma in the left kidney, and the patient was therefore referred for surgical removal of the tumour.

Case 2

A 75 year old woman had been investigated for what was thought …

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