Explanation

Hemoglobin electrophoresis: what is measured?

Hemoglobin is the protein in the red blood cells that carries oxygen. In adults it normally consists mostly of HbA, a small part of HbA2 and hardly any HbF. The test separates these types of hemoglobin and measures how much of each there is; abnormal types, such as HbS in sickle cell disease, also become visible this way. An abnormal composition fits a hemoglobinopathy: a hereditary abnormality of the hemoglobin, as carriership or as a disease.

What can it detect?

Carriership of sickle cell disease (HbS alongside HbA) or of other hemoglobin variants, such as HbC or HbE
Carriership of beta thalassemia (raised HbA2, usually with small red blood cells)
Sickle cell disease or a severe form of thalassemia, which has usually already been discovered through the heel prick or at a young age

Result

What does the result mean?

Positive result

An abnormal result usually means that you are a carrier of a hereditary hemoglobin disorder, such as sickle cell disease or beta thalassemia. Carriers are not ill and usually have no symptoms; beta thalassemia often goes with a slightly low hemoglobin with small red blood cells, and carriers of sickle cell disease can sometimes get symptoms with heavy exertion or at high altitude. Carriership mainly matters when you want to have children: if you and your partner are both carriers, each child has a 1 in 4 chance of sickle cell disease or thalassemia. The result also matters for your parents, brothers, sisters and children, because they may also have the predisposition. Sometimes the result shows the disease itself instead of carriership; that is almost always already known.

Negative result

A normal result means that no sickle cell disease, no beta thalassemia and no other abnormal type of hemoglobin was found. However, carriership of alpha thalassemia usually cannot be seen with this test, because the composition of the hemoglobin is then normal; DNA testing is needed for that. So if you have small red blood cells (a low MCV) without iron deficiency, a normal result does not rule out a hereditary hemoglobin disorder.

After an abnormal result

With carriership, the GP usually advises having the partner tested as well, especially when planning children. If both partners are carriers, a referral to a clinical geneticist (a doctor specializing in hereditary conditions) follows for an explanation of the chance of a child with the disease and the options. With a normal result with small red blood cells without iron deficiency, DNA testing for alpha thalassemia may follow.

Reliability

How reliable is the test?

The test is reliable for showing carriership of sickle cell disease and other hemoglobin variants and, through a raised HbA2, of most forms of beta thalassemia. Alpha thalassemia can usually only be shown with DNA testing. The result is assessed together with the blood count (hemoglobin, MCV) and the ferritin; in case of doubt or when planning children, DNA testing often follows. The Dutch GP guideline (NHG) on anemia names Hb electrophoresis or chromatography, with DNA testing if needed, as the test when a hemoglobinopathy is suspected, especially in people from a risk group or with hereditary anemia in the family.

What can affect the result?

Iron deficiency lowers the HbA2, so carriership of beta thalassemia can be missed; the ferritin must therefore be known.
Carriership of alpha thalassemia usually gives a normal result and can only be shown with DNA testing.
A blood transfusion in the months before the blood draw makes the result unreliable, because the donor blood is measured as well.
Rare variants and combinations of abnormalities call for additional testing in a specialized laboratory.

Who it is for

Who is the test useful for?

Useful for

Useful when planning children or during pregnancy if you or your partner has parents or ancestors from Suriname, the Antilles, countries around the Mediterranean, Africa, Asia or the Middle East, if a hereditary blood disease runs in the family, or if a child turned out to be a carrier at the heel prick. Also useful with small red blood cells (low MCV) without iron deficiency. For people without that ancestry or family history, the chance of carriership is small and the test is usually not needed.

How common is it?

An estimated 1 in 100 people in the Netherlands is a carrier of a hemoglobinopathy. In people with ancestors from areas where malaria occurs or used to occur, such as Suriname, the Antilles, Africa, Turkey, Morocco, the Middle East and Southeast Asia, this is much more common, in some areas 1 in 7. In the Netherlands, about 40 to 60 people with sickle cell disease are discovered every year.

The NHG guideline on anemia and Erfelijkheid.nl (Erfocentrum)

Drawbacks and risks

The result has consequences for blood relatives and for choices about having children; this can cause uncertainty or worry, even if you are not ill yourself.
A normal result can give false reassurance: carriership of alpha thalassemia, and of beta thalassemia with simultaneous iron deficiency, can be missed.

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