Thalassaemia - Diagnosing thalassaemia

Thalassaemia can be diagnosed using a blood test. Further DNA testing may be needed so the exact type of thalassaemia can be determined.

Antenatal screening

The purpose of antenatal screening (screening carried out during pregnancy) is to check for inherited disorders, such as sickle cell anaemia, and to provide parents with the information they need to make informed decisions.

Pregnant women are routinely screened for the thalassaemia trait. If they test positive, their partner will also be offered the test. If both parents have the thalassaemia trait, there's a one in four chance their baby will have thalassaemia.

Further testing is also available to confirm whether your baby will definitely be born with thalassaemia. There are three methods of testing for this:

chorionic villus sampling – a small sample of placenta (the organ that's attached to the womb lining during pregnancy) is removed and tested
amniocentesis – a small sample of amniotic fluid is taken from inside the womb for testing
foetal blood sampling – under local anaesthetic, a small sample of blood is taken from your baby's umbilical cord or from the umbilical vein as it passes through their liver

Counselling

Being told that your baby will be born with thalassaemia can be traumatic and upsetting.

You'll be offered counselling to give you and your partner the opportunity to express your feelings and to ask questions about how the diagnosis may affect you.

The counsellor will tell you about the different options available to allow you to make an informed decision about how to proceed with the pregnancy.

Pre-implantation genetic diagnosis

Pre-implantation genetic diagnosis (PGD) is an option for couples who don't want to give birth to a child with thalassaemia but are unwilling to consider terminating a pregnancy.

PGD is similar to in-vitro fertilisation (IVF). IVF is a method of helping infertile couples conceive by surgically removing an egg from the woman's ovaries and fertilising it with the man's sperm in a laboratory.

As with IVF, PGD involves removing eggs from a woman's ovaries, which are fertilised using a sample of sperm taken from her partner. The fertilised embryo can be tested for thalassaemia. If the results are negative, the embryo can then be implanted into the woman's womb.

PGD is a fairly new procedure that's only available at a number of specialist thalassaemia centres. A list of national sickle cell and thalassaemia centres is available on the Brent Sickle Cell & Thalassaemia Centre website.

After birth

Unlike the related blood disorder sickle cell anaemia, newborn babies aren't routinely screened for thalassaemia. There are two reasons for this:

blood tests are usually unreliable during the first six months of life
unlike sickle cell anaemia, thalassaemia doesn't present an immediate threat to a baby's life – babies born with sickle cell anaemia have a high risk of developing serious infections and need immediate treatment with antibiotics

If your baby starts to develop the symptoms of thalassaemia as they get older, a diagnosis can be confirmed using a blood test.

Assessing iron levels

If you have beta thalassaemia major, you'll need regular blood transfusions, which will increase the level of iron in your body.

To remove the excess iron, a treatment known as chelation therapy will be used. This will prevent serious complications from excess iron occurring, such as heart or liver disease.

Read more about how thalassaemia is treated.

Regular tests to measure your iron levels will be required to monitor the effectiveness of chelation therapy.

Iron levels can be assessed using:

These are outlined below.

Blood tests

Blood tests are an easy way of measuring the amount of iron in your blood. However, they don't indicate how much iron is collecting in certain organs, such as in your brain.

The measurements provided by blood tests can also be distorted by other factors, such as infection.

Blood tests are used to provide a general overview of how well your chelation therapy is working, but they can't be used in isolation.

It's usually recommended that someone with thalassaemia should have a blood test at least every three months.

MRI scans

A magnetic resonance imaging (MRI) scan uses powerful magnetic waves to produce a detailed picture of the inside of your body. MRI scans are able to detect and measure any iron in your organs.

The two organs known to be most vulnerable to the effects of iron are the liver and the heart.

It's usually recommended that you have an MRI scan of your liver at least once a year and an MRI scan of your heart at least once every two years. More frequent scans may be required if high levels of iron are found in your heart and liver.

Liver biopsy

A liver biopsy uses minor surgery to remove a tiny section of your liver to test it for the presence of iron.

An MRI scan is usually preferred to a liver biopsy because it's more convenient for both the doctor and the person having the scan. However, if a detailed assessment of the level of iron in the body is required, a liver biopsy may be necessary.