Sickle cell trait: what it means, and how to get tested in Canada

Most people with sickle cell trait feel completely healthy. That is exactly why so many only find out when a partner tests positive too, or when their child is diagnosed. Knowing your status takes one blood test, and it is one of the most caring things you can do for your future family.

What is sickle cell trait?

Sickle cell trait means you inherited one sickle hemoglobin gene (HbS) from one parent and a typical gene from the other. People with the trait are often called carriers. You do not have sickle cell disease, and most carriers never have symptoms, but you can pass the gene to your children.

Sickle cell disease happens when a child inherits two sickle genes, or one sickle gene and another changed hemoglobin gene, such as hemoglobin C or beta thalassemia. Our plain-language guide explains the types.

Why the odds matter

When two carriers have a child, every pregnancy carries the same odds, no matter how many children they already have:

• A 25 percent chance the child has sickle cell disease
• A 50 percent chance the child has sickle cell trait, like their parents
• A 25 percent chance the child has neither

Who should get tested?

Anyone can carry the trait, but it is most common in families from Africa, the Caribbean, the Middle East, South Asia and the Mediterranean. Testing makes sense if you are in a serious relationship, planning a family, donating blood, or if anyone in your family has the trait or the disease.

If you were born in Canada, you may have been screened as a newborn, but programs started at different times in different provinces, and many adults were born before them or outside Canada. If you are not sure, ask for the test.

How to ask your doctor

Ask your family doctor, a nurse practitioner or a walk-in clinic for a hemoglobin electrophoresis, the blood test that shows which types of hemoglobin you carry. It is quick, and usually covered by your provincial health plan. If you are unsure what to say, any of these reasons is enough:

• I am planning a family and want to know my genotype
• Someone in my family has sickle cell trait or disease
• I am of African, Caribbean, Middle Eastern or South Asian descent

Reading your results

A result showing mostly hemoglobin A with some hemoglobin S usually means sickle cell trait, often written AS. Only hemoglobin A means you are not a carrier (AA). Mostly or only hemoglobin S, or S together with C, points to sickle cell disease and needs follow-up with a hematologist.

If you and your partner both carry the trait, a genetic counsellor can walk you through every option, from pregnancy planning to testing during pregnancy. Our guide to pregnancy and sickle cell is a good next read, and so is dating with sickle cell.

Questions people ask

This article is general information, not medical advice. Talk to your own hematology team about your care. In an emergency, call 911.