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Iron Studies

Iron Deficiency

April 30th, 2020


Iron deficiency may occur due to poor intake, poor absorption or loss of iron. The most common complication of iron deficiency is anaemia, which presents as a microcytic, hypochromic anaemia.


  • Causes of Iron Deficiency

  • Nutritional deficiency
  • Malabsorption - e.g. coeliac disease, gastric surgery, PPIs
  • Blood loss - particularly menstrual and gastrointestinal loss; regular blood donation
  • Pregnancy
Blood loss is the most concerning cause of iron deficiency, most commonly due to menstrual or gastrointestinal loss. Poor iron intake is a common cause of deficiency, and less commonly deficiency can be caused by malabsorption. Iron deficiency may occur in late pregnancy, though the most common obstetric cause of anaemia is haemodilution.


  • Clinical Features of Iron Deficiency

  • History

  • Symptoms of anaemia - fatigue, lethargy, lightheadedness, shortness of breath, chest pain, headache
  • Pica - craving of non-foods such as ice, chalk and dirt
  • Restless legs syndrome
  • Bleeding - trauma, haematemesis, malaena, haematochezia, menorrhagia
  • Plummer-Vinson syndrome: iron deficiency anaemia, dysphagia and oesophageal webs
  • Family history - bowel cancer
  • Examination

  • Signs of anaemia - conjunctival pallor, pale hand creases, tachycardia
  • Koilonychia: spoon-shaped nails
  • Brittle nails
  • Alopecia
  • Atrophic glossitis
  • Angular stomatitis


  • Test Findings in Iron Deficiency

  • Full Blood Count & Film

  • Microcytic, hypochromic anaemia
  • Anisocytosis: variation in red cell size
  • Elliptocytosis: oval-shaped or pencil-shaped cells
  • Target cells: dark central discolouration of cells
  • Thrombocytosis: increased platelet count
  • Iron Studies

  • Reduced ferritin
  • Increased serum transferrin with reduced transferrin saturation
  • Increased soluble transferrin receptor
The most specific marker of iron deficiency is serum ferritin, and as such a reduced serum ferritin makes iron deficiency likely. Ferritin can be elevated in the setting of an acute phase response and can appear normal, though a serum concentration above 100μg/L makes iron deficiency unlikely.
Iron deficiency will present with an elevated serum transferrin and elevated total iron binding capacity; these two measures are proportional to each other and relatively interchangeable. The transferrin saturation (TSat) is the percentage of iron that is bound to transferrin and is reduced in iron deficiency, though inflammation, infection and malignancy can also reduce the TSat.
Serum iron (Fe3+) concentration tends to fluctuate with iron intake, acute and chronic disease and in itself is a poor marker of iron status.
The anaemia of iron deficiency tends to be microcytic and hypochromic and the blood film may exhibit poikilocytic changes such as target cells or elliptocytes. Often in early iron deficiency the anaemia is normocytic, with anisocytosis (i.e. an elevated RDW) due to a mix of normocytic and microcytic cells.
If iron deficiency is suspected but not confirmed, improvement in haemoglobin following a trial of iron supplementation can clinch the diagnosis.
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