Sickle Cell Test

The test is used to detect the presence of Haemoglobin S (HbS); this is a variant form of haemoglobin. In healthy individuals, various forms of haemoglobin, including haemoglobin A, haemoglobin A2 and haemoglobin F, are present in small amounts. Haemoglobin S is a genetic abnormality, which causes the shape of the red blood cell to change; this affects the cell’s ability to transport oxygen around the body. Sickle cell disease is inherited; if a child has sickle cell disease, this means they have inherited an HbS gene from each parent.

When is the test used?

The test is used to detect the presence of HbS; the results will also determine the amount of HbS.

The test is usually used as a screening test for babies; sickle cell disease is an inherited condition, if one gene is inherited this indicates that the individual has the trait but if two genes are inherited, this means that the individual has sickle cell disease. Screening is sometimes recommended for those who are at high risk of having a child with sickle cell disease; people of African heritage are usually advised to have the test before they think about starting a family as 25 percent of people with African ancestry have at least one inherited gene.

How is the test done?

The test is done by collecting and analysing a sample of the patient’s blood; a needle is inserted into the vein and the blood is drawn out using a syringe. Once the sample has been collected it will be bottled, labelled and sent away for analysis.

In young children and babies, the blood may be taken from the fingertip or the heel, as this is less traumatic for the child; a needle is used to prick the finger or heel and the blood is collected.

What do the test results mean?

If the test result is negative, this indicates that the patient does not have an inherited gene, meaning that they do not have the trait or the disease.

If the test is positive, this means that further tests will be ordered; the tests will be used to determine whether the individual has one or two copies of the gene.

If the patient has one copy, this means that they have the trait; most people never suffer any symptoms and live perfectly normal lives. If the patient has two copies of the gene, this means that they have sickle cell disease and a large proportion of their haemoglobin will be HbS. Some people with sickle cell disease do not suffer any symptoms; however, they may develop symptoms, including joint and abdominal pain, seizures and a soaring temperature, if they are suffering with an infection or illness.

Specific Blood Tests

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