Haemoglobin variants on testing

Haemoglobin variants are genetic differences in the structure of haemoglobin, the protein in red blood cells that carries oxygen, some of which are picked up incidentally during routine blood testing such as an HbA1c or full blood count. Common examples include sickle cell trait, thalassaemia trait, and other less common structural variants. Many variants cause no symptoms and are only noticed because of how they affect certain laboratory test results.

They are caused by inherited genetic differences in the genes coding for haemoglobin, often carried without symptoms if only one copy of the altered gene is inherited (carrier or "trait" status). Some variants are more common in people with family origins from certain parts of the world, such as sickle cell trait being more common in people of African, Caribbean, and some Mediterranean and Asian backgrounds. They are present from birth as an inherited trait rather than something acquired later.

Most simple carrier states (trait forms) cause no symptoms at all and are only discovered through blood testing done for another reason, or specific screening such as before pregnancy or surgery. Some variants can, however, interfere with the accuracy of certain tests, such as giving a falsely altered HbA1c reading in diabetes monitoring. Rarely, carrying two copies of certain variants (rather than just one) can cause a clinical condition, such as sickle cell disease or thalassaemia major.

For most people, being a carrier (having just one copy) of a haemoglobin variant is not dangerous and does not cause health problems day to day. The main relevance is for family planning, since if both parents carry a variant, there is a chance of a child inheriting two copies and having a more significant blood condition, and for ensuring other blood tests, like HbA1c, are interpreted correctly. Genetic counselling can clarify individual risk if both partners in a couple are found to be carriers.

Yes, haemoglobin variants are inherited genetic traits passed down from parents. If you are found to carry a variant, it can be useful for family members, and any partner if you are planning a pregnancy, to also be tested. This helps identify any risk of a child inheriting a more significant form of the condition if both parents are carriers.

Your doctor will explain which specific variant was found and whether it has any clinical significance, such as affecting the accuracy of other tests or being relevant for family planning. Further testing of family members or a partner may be recommended in certain situations, particularly around pregnancy planning. In most cases, no ongoing monitoring or treatment is needed for a simple carrier state itself.

A simple carrier trait typically needs no treatment, since it does not cause a clinical blood disorder on its own. If a more significant condition, such as sickle cell disease or thalassaemia major, is diagnosed (from inheriting two copies of relevant variants), this is managed with condition-specific treatment by a haematology specialist. Genetic counselling, rather than medical treatment, is usually the main relevant service for carriers themselves.

Carrying one copy of a variant gene (trait or carrier status) generally causes no symptoms and is compatible with completely normal health, whereas inheriting two copies (one from each parent) can cause a clinical disease, such as sickle cell disease or thalassaemia major, with significant health implications requiring ongoing specialist care. This is why carrier testing and genetic counselling for couples planning a pregnancy is valuable, particularly in populations where certain variants are more common. A simple blood test can clarify carrier versus disease status.

Discuss it with a doctor or genetic counsellor if you are planning a pregnancy and have been found to carry a variant, particularly if your partner may also be a carrier, or if you want to understand the implications for other blood tests you have done. A private haematology or genetics consultation can typically be arranged within about one to two weeks. This is especially worthwhile before conceiving, so that any risk to a future child can be discussed and understood in advance.