Fróđleikur: Many different types of hemoglobin (Hb) exist. The most common ones are HbA, HbA2, HbF, HbS, HbC, HbH, and HbM. Healthy adults only have significant levels of only HbA and HbA2.
Some people may also have small amounts of HbF. This is the main type of hemoglobin in an unborn baby's body. Certain diseases are associated with high HbF levels (when HbF is more than 2% of the total hemoglobin).
HbS is an abnormal form of hemoglobin associated with sickle cell anemia. In people with this condition, the red blood cells sometimes have a crescent or sickle shape. These cells easily break down or can block small blood vessels.
HbC is an abnormal form of hemoglobin associated with hemolytic anemia. The symptoms are much milder than they are in sickle cell anemia.
Other, less common, abnormal Hb molecules cause other types of anemia.
In adults, these are normal percentages of different hemoglobin molecules:
In infants and children, these are normal percentage of HbF molecules:
- Hb A: 95% to 98%
- Hb A2: 2% to 3%
- Hb F: 0.8% to 2%
- Hb S: 0%
- Hb C: 0%
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different samples. Talk to your provider about the meaning of your specific test results.
- Hb F (newborn): 50% to 80%
- Hb F (6 months): 8%
- Hb F (over 6 months): 1% to 2%
What Abnormal Results Mean
Significant levels of abnormal hemoglobins may indicate:
You may have false normal or abnormal results if you have had a blood transfusion within 12 weeks of this test.
Sickle cell anemia
Sickle cell anemia is a disease passed down through families. The red blood cells that are normally shaped like a disc take on a sickle or crescent shape. Red blood cells carry oxygen throughout the body.
- Hemoglobin C disease
- Rare hemoglobinopathy
- Sickle cell anemia
- Inherited blood disorder in which the body makes an abnormal form of hemoglobin (thalassemia)
Sickle cell anemia is caused by an abnormal type of hemoglobin called hemoglobin S. Hemoglobin is a protein inside red blood cells that carries oxygen.
Sickle cell anemia is inherited from both parents. If you get the sickle cell gene from only 1 parent, you will have sickle cell trait. People with sickle cell trait do not have the symptoms of sickle cell anemia.
- Hemoglobin S changes the red blood cells. The red blood cells become fragile and shaped like crescents or sickles.
- The abnormal cells deliver less oxygen to the body's tissues.
- They can also easily get stuck in small blood vessels and break into pieces. This can interrupt healthy blood flow and cut down even more on the amount of oxygen flowing to body tissues.
Sickle cell disease is much more common in people of African and Mediterranean descent. It is also seen in people from South and Central America, the Caribbean, and the Middle East.
Symptoms usually do not occur until after the age of 4 months.
Almost all people with sickle cell anemia have painful episodes called crises. These can last from hours to days. Crises can cause pain in the lower back, leg, joints, and chest.
Some people have 1 episode every few years. Others have many episodes each year. The crises can be severe enough to require a hospital stay.
When the anemia becomes more severe, symptoms may include:
Younger children with sickle cell anemia have attacks of abdominal pain.
- Rapid heart rate
- Shortness of breath
- Yellowing of the eyes and skin (jaundice)
The following symptoms may occur because small blood vessels become blocked by the abnormal cells:
Over time, the spleen stops working. As a result, people with sickle cell anemia may have symptoms of infections such as:
- Painful and prolonged erection (priapism)
- Poor eyesight or blindness
- Problems with thinking or confusion caused by small strokes
- Ulcers on the lower legs (in adolescents and adults)
Other signs and symptoms include:
- Bone infection (osteomyelitis)
- Gallbladder infection (cholecystitis)
- Lung infection (pneumonia)
- Urinary tract infection
Exams and Tests
- Delayed growth and puberty
- Painful joints caused by arthritis
- Heart or liver failure due to too much iron (from blood transfusions)
Tests commonly done to diagnose and monitor people with sickle cell anemia include:
Thalassemia is a blood disorder passed down through families (inherited) in which the body makes an abnormal form of hemoglobin. Hemoglobin is the protein in red blood cells that carries oxygen. The disorder results in large numbers of red blood cells being destroyed, which leads to anemia.
Hemoglobin is made of 2 proteins:
Thalassemia occurs when there is a defect in a gene that helps control production of 1 of these proteins.
There are 2 main types of thalassemia:
Alpha thalassemias occur most often in people from Southeast Asia, the Middle East, China, and in those of African descent.
- Alpha thalassemia occurs when a gene or genes related to the alpha globin protein are missing or changed (mutated).
- Beta thalassemia occurs when similar gene defects affect production of the beta globin protein.
Beta thalassemias occur most often in people of Mediterranean origin. To a lesser extent, Chinese, other Asians, and African Americans can be affected.
There are many forms of thalassemia. Each type has many different subtypes. Both alpha and beta thalassemia include the following 2 forms:
You must inherit the gene defect from both parents to develop thalassemia major.
- Thalassemia major
- Thalassemia minor
Thalassemia minor occurs if you receive the faulty gene from only 1 parent. People with this form of the disorder are carriers of the disease. Most of the time, they do not have symptoms.
Beta thalassemia major is also called Cooley anemia.
Risk factors for thalassemia include:
- Asian, Chinese, Mediterranean, or African American ethnicity
- Family history of the disorder
The most severe form of alpha thalassemia major causes stillbirth (death of the unborn baby during birth or the late stages of pregnancy).
Children born with beta thalassemia major (Cooley anemia) are normal at birth, but develop severe anemia during the first year of life.
Other symptoms can include:
People with the minor form of alpha and beta thalassemia have small red blood cells but no symptoms.
Exams and Tests
Your health care provider will do a physical exam to look for an enlarged spleen.
A blood sample will be sent to a laboratory to be tested.
- Red blood cells will appear small and abnormally shaped when looked at under a microscope.
- A complete blood count (CBC) reveals anemia.
- A test called hemoglobin electrophoresis shows the presence of an abnormal form of hemoglobin.
- A test called mutational analysis can help detect alpha thalassemia.