Genetic Testing for Sickle Cell & Thalassaemia

What is Sickle Cell and Thalassaemia?

These are two genetically inherited conditions that affect the blood, see Inheritance of Haemoglobin. To find out if a person has inherited any of these conditions they need to have a special blood test.

How is testing done for Sickle Cell & Thalassaemia?

When a person goes to a specialist Centre, such as Brent Sickle Cell & Thalassaemia Centre, for a blood test, they are given information about Sickle Cell, Thalassaemia and any other common unusual haemoglobin. They are told how these genetic conditions are inherited and what it means if someone has any of them. The person then has an opportunity to decide if they wish to be tested or not.

To help a person decide whether they should be tested or not the nurse will explain the test, ask a few questions about the person’s family origin, once the person has understood the information given and they still wish to have the test done they will be asked to sign a form giving their permission for the blood to be taken and sent for testing.

The session at the Centre takes about thirty minutes, the time includes time taken to give the person information, filling in the blood test form, taking the blood from the arm using a small sterile needle and answering any questions the person may have.

What happens in the laboratory?

The blood sample is sent to the laboratory for the special blood test. It will take about five to ten days for the result to be ready and sent back to the Centre or to the clinic that sent the sample.

When will I get the result?

The result will be sent to you within two to four weeks no matter what the result is even if it is the usual haemoglobin or a healthy carrier like sickle cell trait; a special card will be sent which will have the result on it. If necessary you will also be sent a leaflet which explains the healthy carrier gene found.

If you are found to have two unusual haemoglobins, for example, Hb SC which is a type of sickle cell disease, a specialist nurse will contact you and arrange for you to attend for genetic counselling and will advise about the on-going medical care you will need.

You can also contact the Centre to arrange for your partner and other members of your family to be tested.

Who will be told my result?

All your personal details are CONFIDENTIAL and no one other than staff at the Centre or the clinic where you have been tested and the laboratory will see your personal details or your blood test result. By law, health workers have to keep all your information confidential and they cannot give your result to anyone else unless you have given them permission to do so. You have the right to ask to see the information kept about you in the Centre or any health clinic including your GP surgery.

You will be sent a photocopy of your test result and a letter to give to your GP to keep in your medical records because this information may be important to your health and to you and your partner when you want to have children.

The result will only be given to other agencies if you have requested it and have given consent for us to do so. For example, some patients request their results to be given to the housing department in support of their application for re-housing.

If after reading this information you feel you need more information you can contact the Centre for an appointment.

Commonly asked questions

Is the test painful?

You will feel a sharp pin prick pain when the needle is put in the arm to take the blood, but this will only lasts a few seconds and once the blood is taken you should not feel any more pain.

Can I be sure that the blood test is safe?

People may worry about contamination and infection but in the UK a new sterile needle is used for each person when taking blood and the person doing the blood test wears rubber gloves to help prevent risk of infection.

Will the test show my blood group?

The test for sickle cell and Thalassaemia are specific blood tests and unless one takes blood to test for blood grouping specifically it will not be tested for routinely.

I have had a blood test before will this not have shown if I have Sickle Cell or Thalassaemia?

You may have had blood tests for a number of reasons in the past but it does not mean you have been tested for sickle cell and Thalassaemia. This blood test would only be done by the laboratory if blood has been sent in the right type of blood bottle and this test has been requested specifically.

I was tested in my country and told I am alright, why should I be tested again?

It is not uncommon for the blood tests done abroad to be inaccurate. If a person went for a blood test to see if they have sickle cell disease the result may show that they do not have sickle cell disease and the person giving the result may just say the result is ‘normal’ meaning the person does not have a disease, however if they have sickle cell trait and they will not be told this necessarily since they are healthy and do not have an illness. However, having sickle cell trait is important when the individual wants to have children.

Some people may have misunderstood the result they were given and knowing that they do not have the disease they may assume that this means they have a ‘normal’ result which excludes being a carrier.

Some laboratories in developing countries may use out of date or faulty equipment and get false negative results. It is not uncommon for an individual to believe they have normal haemoglobin when in fact they have sickle cell trait or any other unusual haemoglobin and it is when they have a child born with sickle cell disease that they discover the error.

Who can be tested?

Anyone can be tested for sickle cell and thalassaemia including men, women and children.

However, in the case of children it is usually better to get the two parents (adults) tested to see if they carry any unusual haemoglobin. If both parents do not carry any unusual haemoglobin then they will know their children are not at-risk of inheriting a disease; even if one parent is a carrier the most their children can inherit is a trait (be a carrier), see Inheritance of Haemoglobin. In this instance it is better not to put the child through having a blood test but wait until the child reaches puberty, or early adulthood when they start courting, want to get married or start having children that is the time being a carrier becomes most important. It is also important if they need to have general anaesthetic for an operation then they need to be tested for the sickle cell gene, see Haemoglobin S - Sickle Cell - Importance of Sickle Cell Trait.

All babies born in England are offered testing for sickle cell disease when they are 5 – 8 days old, see Newborn Screening, as part of the heel prick test, but this does not test for Thalassaemia.

If a couple both have any unusual haemoglobin and they want to have children

If a couple both have any unusual haemoglobin they may or may not be at risk of having a child with a disease. It is important to know which type of unusual haemoglobin the couple have in order to work out whether their children are at-risk of having a disease. This should be discussed with the persons GP, Nurse, Midwife or contact one of the specialist National Sickle Cell / Thalassaemia Centres.