Hemoglobinopathy Screening
Hemoglobin screening 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 is usually done with your first prenatal blood work.
How are hemoglobin disorders inherited?
Hemoglobin disorders occur when a person inherits two abnormal hemoglobin traits, one from each parent. When both parents have a hemoglobin trait each child has a 25% chance to be born with a hemoglobin disorder. This type of inheritance is called autosomal recessive.
How do I find out if my child could have an inherited blood disease?
Prenatal blood tests are reviewed by a program coordinator. You are contacted by a genetic counselor if you have a trait that needs follow-up. Testing is offered to the father of the baby to find out if your baby is at risk for a hemoglobin disorder. If you and the father of the baby both carry a hemoglobin trait, you are offered genetic counseling and may be offered prenatal diagnosis. Newborns in California are routinely tested for hemoglobin disorders.
What medical problems are caused by a hemoglobin disease?
The medical problems depend on the specific hemoglobin disorder. Some hemoglobin disorders cause prenatal death or infant death, or life-long medical problems that require frequent medical care. Other types of hemoglobin disorders cause very few problems and need little to no medical care.
__________________________________________
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 routinely makes three types of hemoglobin by combining different proteins (alpha chains, beta chains, delta chains, gamma chains).
• Hb A: This is the most common type of hemoglobin in humans. More than 95% of hemoglobin is typically Hb A. Hb A combines two alpha chains (α2) and two beta chains (β2).
• Hb A2: This type of hemoglobin is made in much smaller amounts than Hb A. Usually, less than 3% of hemoglobin is Hb A2. Hb A2 combines two alpha chains and two delta chains.
• Hb F: This is the main hemoglobin during fetal life. After birth, Hb F slowly decreases. Hb F makes up less than 2% of adult hemoglobin. Hb F combines two alpha chains and two gamma chains.
The genetic instructions for hemoglobin come from your parents. These instructions are called genes. The four proteins that make up hemoglobin are each made by a different gene. Changes in these genes can affect the structure, stability, behavior, or production of hemoglobin.
Hemoglobin traits are found in people from all parts of the world and rarely cause health problems. Most people are unaware they carry a hemoglobin trait unless special testing is ordered.
Variant Hemoglobins: Hemoglobins that have a change in their structure are called "variants". More than 500 variant hemoglobins have been reported worldwide. Some variants make a slightly different type of hemoglobin but do not cause hemoglobin disorders. When a variant is co-inherited with Hb A, it is called a hemoglobin "trait". When a variant is co-inherited with another variant or the same variant, it may cause a hemoglobin disorder.
One example of a common hemoglobin variant is sickle hemoglobin (Hb S), which causes sickle cell anemia. Like many hemoglobin traits, Hb 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.
Cther common hemoglobin variants:
• Hb C
• Hb D
• Hb E
Click here for more information about sickle cell and related traits from the Centers for Disease Control (CDC)
Thalassemias: Genetic changes that affect the production of hemoglobin are called thalassemias. These genetic changes cause the body to make less of one of the protein chains that form hemoglobin. The body can still make all three types of hemoglobins (A, A2 and F), but the red blood cells are often smaller than usual. 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 main types of thalassemia are alpha thalassemia and beta thalassemia.
• Alpha thalassemia
• Beta thalassemia
Click here for more information about thalassemia.
Last reviewed: March 19, 2021
Reviewed by: Catherine Klumpp, MS, LCGC; Kimberly Barr, LCGC