Thalassaemia

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Laboratory Tests

   FBC (full blood count). The FBC is a snapshot of the cells and fluid in your bloodstream. Among other things, the FBC will tell the doctor how many red blood cells are present, how much haemoglobin is in them, and give the doctor an evaluation of the size and shape of the red blood cells present. MCH (mean corpuscular haemoglobin) and MCV (mean corpuscular volume) are measurements of the haemoglobin content and size of the red blood cells. A low MCH or MCV is often the first indication of thalassaemia. If the MCH or MCV is low and iron-deficiency has been ruled out, the person may be a thalassaemia trait carrier.

Blood film (smear). In this test a thin stained layer of blood is examined on a slide, under a microscope. The number and type of white blood cells, red blood cells, and platelets can be manually counted and be evaluated to see if they are normal and mature. A variety of disorders affect normal blood cell production. With thalassaemia, the red blood cells are often microcytic (small). They may also be:

  • Hypochromic (pale – indicating less haemoglobin)
  • Vary in size (anisocytosis) and shape (poikilocytosis)
  • Be nucleated (not normal in a mature RBC)
  • Be distorted to produce “target cells”, which look like a bull’s-eye under the microscope.

Iron studies. These may include: Iron, Ferritin, UIBC, TIBC, and Percent Saturation of Transferrin. These tests measure different aspects of the body’s iron storage and usage. They are ordered to help determine whether an iron deficiency is causing and/or exacerbating a patient’s Anaemia. One or more of them may also be ordered to help monitor the degree of iron overload in a patient with thalassaemia.

Haemoglobinopathy (Hb) evaluation. This test measures the type and relative amounts of haemoglobins present in the red blood cells. Haemoglobin A, composed of both alpha and beta globin, is the major normal type of haemoglobin found in adults. A greater percentage of HbA2 and/or HbF is usually seen in beta thalassaemia trait. HbH may be seen in alpha thalassaemia , but only when at two of the four alpha genes are deleted or mutated.

DNA analysis. This test is used to investigate deletions and mutations in the alpha and beta globin producing genes. Family studies can be done to evaluate carrier status and the types of mutations present in other family members. DNA testing is not routinely done but can be used to help diagnose thalassaemia, and to determine carrier status. It is the only reliable way of diagnosing carriers who have only one of four alpha genes deleted or mutated.

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