Haematology - Iron deficiency anaemia

Question 1

What broadly are the causes of iron deficiency?

Answer 1

Insufficient dietary iron

Increased iron requirements e.g. pregnancy

Iron being lost e.g. bleeding

Inadequate iron absorption

Question 2

How is dietary iron typically absorbed? And what conditions/medications can impact it?

Answer 2

Iron is mainly absorbed in the duodenum and jejunum.

It requires the acid from the stomach to keep the iron in the soluble ferrous (Fe2+) form. When the acid drops it changes to the insoluble ferric (Fe3+) form. Therefore, PPIs can interfere with iron absorption.

Conditions that result in inflammation of the duodenum or jejunum such as coeliac disease or Crohn’s disease can also cause inadequate iron absorption.

Question 3

What is the most common cause of iron deficiency anaemia?

Answer 3

Blood loss

This is commonly from:

• Menstruation
• Blood loss from the GI tract e.g. oesophagitis/gastritis (most common), IBD and GI cancers

Question 4

How is iron transported around the body?

Answer 4

Bound to a carrier protein called transferrin

Question 5

What is included in iron studies

Answer 5

Ferritin

• form that iron takes when it is deposited and stored in cells
• Low ferritin highly suggestive of iron deficiency anaemia
• High ferritin difficult to interpret - likely to be due to inflammation rather than iron overload (ferritin released from cells in inflammation)

Serum iron:

• Varies significantly throughout the day
• Not useful measure on its own of iron levels

TIBC:

• Marker for amount of transferrin in serum
• Increased in iron deficiency
• Decreased in iron overload

Transferrin saturation:

• Good indication of total iron in the body
• Normally around 30%
• If iron is low, transferrin saturation will be lower
• Higher saturation at higher levels of iron
• Fasting samples give most accurate results, to avoid the increase caused by dietary iron

Question 6

Management of iron deficiency anaemia

Answer 6

The anaemia can be treated depending on the severity and symptoms with three methods, that range from fastest to slowest and most invasive to least invasive:

Blood transfusion. This will immediately correct the anaemia but not the underlying iron deficiency and also carries risks.

Iron infusion e.g. “cosmofer”. There is a very small risk of anaphylaxis but it quickly corrects the iron deficiency. It should be avoided during sepsis as iron “feeds” bacteria.

Oral iron e.g. ferrous sulfate 200mg three times daily. This slowly corrects the iron deficiency. Oral iron causes constipation and black coloured stools. It is unsuitable where malabsorption is the cause of the anaemia.

Question 7

How quickly does haemoglobin typically rise when correcting iron-deficiency anaemia?

Answer 7

by around 10 grams/litre per week.