Q&A: Interpretation of Iron Studies

A tight regulation of iron balance is essential to avoid both iron deficiency and overload. The regulation of iron metabolism involves the interaction of a number of specific proteins as well as the interplay between iron absorption, recycling, and iron loss. Disorders of iron balance, both iron deficiency and iron overload, could result from a disruption of this delicate balance.

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This is a Question & Answer revision article designed for medical students and professionals preparing for the PLAB, MRCP or USMLE examinations. They are based on actual questions from these examinations. You may find the What Is Blood? article more useful, or one of our many articles on Diseases & Conditions, Medical Syndromes, Health & Wellness or Home Remedies.

In this article:
Application of iron studies
MCQ: clinical scenario
MCQ: answer
MCQ: explanation

Application of iron studies

The assessment of iron deficiency or overload may be complicated by the presence of an acute phase response or hepatocellular disease. In general, serum ferritin is the preferred test for the assessment of iron deficiency, however levels may be normal (up to 100 µg/L) when iron deficiency coexists with an acute phase response. Soluble transferrin receptor levels are not affected in an acute phase response; levels are normal in anaemia of chronic disease uncomplicated by iron deficiency. An alternative approach to the patient with suspected iron deficiency and/or chronic inflammatory disease is to assess the haemoglobin response to iron therapy.

MCQ: clinical scenario

Consider the following values.

MCV: Decreased; Serum ferritin: Increased; Total iron binding capacity: Normal; Serum iron: Increased; Marrow iron: Present.

The most likely diagnosis is:

a) Thalassaemia trait
b) Hypoparathyroidism
c) Hereditary sideroblastic anaemia
d) Anaemia of chronic disease
e) Iron deficiency anaemia

MCQ: answer

The correct answer is C

MCQ: explanation

Patients with a defect in mitochondrial function resulting in a sideroblastic anaemia can also present with a microcytic, hypochromic anaemia. Hereditary sideroblastic anaemia is a rare condition that presents in childhood either as an X-linked or autosomally inherited condition. Red blood cell morphology is typically dimorphic, and measurements of iron supply make the distinction from iron deficiency quite easy. Patients who develop an acquired ringed sideroblastic anaemia typically exhibit excessive iron accumulation, even to the point of tissue iron overload. Their red blood cell morphology can be quite variable, while marrow morphology demonstrates the pathognomonic finding of ringed sideroblasts.

	Iron deficiency	Anaemia of chronic disease	Iron deficiency and inflammation	Acute phase response	Iron overload
Serum iron	Decreased	Decreased	Decreased	Decreased	Increased
Serum transferrin, Total iron binding capacity (TIBC)	Increased	Decreased	Decreased (low normal)	Decreased	Decreased or normal
Transferrin saturation	Decreased	Decreased	Normal or decreased	Decreased	Increased
Serum ferritin	Decreased	Normal (> 100 ug/l )	“Normal”	Increased	Increased
Soluble transferrin receptor	Increased	Normal	Increased	Normal	Decreased

Also see the separate Q&A article, Interpreting Iron Studies.

Reference(s)
1). Royal College of Pathologists of Australasia (RCPA): Iron studies. Available online: https://www.rcpa.edu.au/Manuals/RCPA-Manual/Pathology-Tests/I/Iron-studies