Genetics Northern California

Hemoglobinopathy Screening

Hemoglobinopathies are inherited blood diseases that cause severe anemia and related medical problems. Anemia is a condition in which the body does not have enough healthy red blood cells. At Kaiser Permanente, we routinely screen for these types of genetic blood diseases during pregnancy. Every pregnant woman has a routine blood test to look for anemia. More tests are done when the red blood cells look smaller than usual, or if screening is requested by the woman based on her ethnicity.  Follow-up testing includes iron studies and a special blood test called hemoglobin electrophoresis. DNA testing may also be done when needed. With these tests, our screening program can find almost all women who carry a hemoglobin (blood) trait and identify couples whose children could be born with a blood disease. 
 
When can I have screening?
How is this type of blood disease inherited?
How do I find out if my child could have an inherited blood disease?
What medical problems are caused by a hemoglobin disease?
 
More about hemoglobin and hemoglobin traits

When can I have screening?

Hemoglobin screening can be done at any time, but it is most useful when you are planning a pregnancy or in the first few months of pregnancy (before 20 weeks). At Northern California Kaiser Permanente, screening usually starts with your first prenatal blood work.

How is this type of blood disease inherited?
Almost all hemoglobin diseases are inherited in an autosomal recessive  manner.  These conditions show up when a person inherits two hemoglobin traits, one from each parent. This can only happen when both parents carry the same (or similar) trait. When both parents have a hemoglobin trait there is a 25% chance of having a child with a blood disease in any pregnancy.

AfricanAm Newborn and MomHow do I find out if my child could have an inherited blood disease? 
If your blood test suggests you might carry a hemoglobin trait, the results are reviewed by a program coordinator. Results that need follow-up are sent to one of five Northern California Genetics Centers. A genetic counselor contacts you to offer a blood test to the father of the baby. Even if you have a hemoglobin trait, your baby is only at risk for an inherited blood disease when the father of the baby ALSO carries a hemoglobin trait. Couples found to be at risk are offered genetic counseling and may be offered prenatal diagnosis. Testing for hemoglobin diseases are also a routine part of newborn screening in California. 

What medical problems are caused by a hemoglobin disease?
The medical problems caused by a hemoglobin disease are extremely variable. Some of these diseases cause prenatal death or infant death. Other blood diseases lead to life-long medical problems and the need for frequent medical care. Still other types of inherited blood diseases are very mild and have few medical problems. The kinds of problems that may happen depend on the specific hemoglobin disease.

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Red blood cellsMORE ABOUT: Hemoglobin and Hemoglobin Traits
Hemoglobin

Our blood is made up of trillions of red blood cells. Each red blood cell contains iron and a protein called hemoglobin that carries oxygen through the body. Our body usually makes three different types of hemoglobin. All three types are found in the red blood cells.

Hemoglobin A: This is the most common type of hemoglobin in humans. Hemoglobin A is a made from proteins made by the body called alpha chains and beta chains. Hemoglobin A has two alpha chains (α2) and two beta chains (β2). More than 95% of hemoglobin is typically hemoglobin A
•  Hemoglobin A2: This type of hemoglobin is made in much smaller amounts than hemoglobin A. There is usually less than 3% of hemoglobin A2 found in the red blood cells. Hemoglobin A2 has two alpha chains and two delta chains, which is what makes it different from hemoglobin A.
•  Hemoglobin F: This is another common type of hemoglobin found in even smaller amounts than hemoglobin A2. Hemoglobin F is the main hemoglobin during fetal life. After birth, hemoglobin F decreases slowly and eventually makes up less than 2% of the total hemoglobin. It is made of two alpha chains and two gamma chains.

The genetic instructions for hemoglobin come from your parents. These instructions are called ‘genes’. There are separate genes for each protein (alpha chains, beta chains, delta chains, and gamma chains) that make up the different types of hemoglobin. When a genetic change affects the type of hemoglobin or the amount of hemoglobin being made, it is called a hemoglobin trait.

Hemoglobin traits

Hemoglobin traits are found in people from all parts of the world and rarely cause health problems. Most people are completely unaware that they carry a hemoglobin trait, unless special testing is ordered. Blood tests may show minor differences, such as mild anemia or small red blood cells. There are two main types of hemoglobin traits: hemoglobin variants and thalassemias. A person with a hemoglobin variant has a different type of hemoglobin in their blood. A person with a thalassemia trait has the usual types of hemoglobin, but one part of the hemoglobin is made in lower amounts.

Hemoglobin Variants: Most people have just the three common types of hemoglobin in their blood. When a hemoglobin trait affects the shape of hemoglobin or the way it works, it is called a variant. This means the body makes a less common type of hemoglobin than three listed above. More than 500 different variants have been reported worldwide. Most variants are caused by a genetic change in the instruction for the beta chains found in hemoglobin A; but variants can affect any of the proteins that make hemoglobin. Not all variants cause inherited blood diseases. Many variants make a slightly different type of hemoglobin but have no effect on the way it works.

An example of a common hemoglobin variant is sickle hemoglobin (hemoglobin S), which causes sickle cell anemia. Like many hemoglobin traits, hemoglobin S is seen more often in people whose ancestors lived in parts of the world where malaria is found. This includes Africa, South America, Latin America, the West Indies, the Middle East, Greece, Spain, Italy, Turkey, and areas around the Mediterranean Sea. In the United States, one out of every 10 African-Americans has sickle cell trait, and one out of every 400 African-Americans has sickle cell disease.

Common hemoglobin variants:

Sickle cell (hemoglobin S)
Hemoglobin E
Hemoglobin C
• More information about sickle cell and related traits is available at: http://www.cdc.gov/ncbddd/sicklecell/documents/SCD%20factsheet_Sickle%20Cell%20Trait.pdf

Thalassemias: For some people, a genetic change means they make less of one of the protein chains that form hemoglobin. While the body still makes all three of the usual hemoglobins (A, A2 and F), the red blood cells are often smaller than usual. This type of hemoglobin trait is called "thalassemia". Thalassemia traits are more common in people whose ancestors come from Cyprus, Greece, Italy, Turkey, the Arabian Peninsula, and parts of Asia (including India, Pakistan, Southern China, Thailand, the Philippines, Cambodia, Vietnam and Laos). It is also found in people with ancestry from Africa and the West Indies. It is estimated that two million people in the United States have a thalassemia trait.

The two most common types of thalassemia are alpha thalassemia and beta thalassemia.

Alpha thalassemia
Beta thalassemia
• More information about thalassemia is available at: http://www.thalassemia.org/



Last reviewed: June 25, 2015
Reviewed by: Bruce Haas, LCGC; Kimberly Barr, LCGC; Mark Lipson, MD