Hemophilia screening
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Hemophilia screening On the Web |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
- In the United States, most people with hemophilia are diagnosed at a very young age. The median age at diagnosis is 36 months for people with mild hemophilia, 8 months for those with moderate hemophilia, and 1 month for those with severe hemophilia. In about two thirds of cases, there is a family history of hemophilia. The diagnosis of hemophilia is made using a special blood test and most babies can be tested soon after birth. Sometimes prenatal genetic testing is done to diagnose hemophilia before birth. For the one-third of babies born with hemophilia in families with no known history of hemophilia, the diagnosis is made when an unusual bleeding event occurs. Special blood tests are required to make the diagnosis. If you or your child appears to have a bleeding problem, your doctor will ask about your personal and family medical histories. This will reveal whether you or your family members, including women and girls, have bleeding problems. However, some people who have hemophilia have no recent family history of the disease.
- You or your child also will likely have a physical exam and blood tests to diagnose hemophilia. Blood tests are used to find out:
- How long it takes for your blood to clot
- Whether your blood has low levels of any clotting factors
- Whether any clotting factors are completely missing from your blood
- Pregnant women who are known hemophilia carriers can have the disorder diagnosed in their unborn babies as early as 12 weeks into their pregnancies. Women who are hemophilia carriers also can have "preimplantation diagnosis" to have children who don't have hemophilia.For this process, women have their eggs removed and fertilized by sperm in a laboratory. The embryos are then tested for hemophilia. Only embryos without the disorder are implanted in the womb.Many people who have or have had family members with hemophilia will ask that their baby boys get tested soon after birth. About one-third of babies who are diagnosed with hemophilia have no other family members with the disorder. A doctor might check for hemophilia if a newborn is showing certain signs of hemophilia. Diagnosis includes screening tests and clotting factor tests. Screening tests are blood tests that show if the blood is clotting properly. Clotting factor tests, also called factor assays, are required to diagnose a bleeding disorder. This blood test shows the type of hemophilia and the severity.
Families With a History of Hemophilia
Any family history of bleeding, such as following surgery or injury, or unexplained deaths among brothers, sisters, or other male relatives such as maternal uncles, grandfathers, or cousins should be discussed with a doctor to see if hemophilia was a cause. A doctor often will get a thorough family history to find out if a bleeding disorder exists in the family. Many people who have or have had family members with hemophilia will ask that their baby boys get tested soon after birth. In the best of cases, testing for hemophilia is planned before the baby’s delivery so that a sample of blood can be drawn from the umbilical cord (which connects the mother and baby before birth) immediately after birth and tested to determine the level of the clotting factors. Umbilical cord blood testing is better at finding low levels of factor VIII (8) than it is at finding low levels of factor IX (9). This is because factor IX (9) levels take more time to develop and are not at a normal level until a baby is at least 6 months of age. Therefore, a mildly low level of factor IX (9) at birth does not necessarily mean that the baby has hemophilia B. A repeat test when the baby is older might be needed in some cases. Learn more about the inheritance pattern for hemophilia.
Families With No Previous History of Hemophilia
About one-third of babies who are diagnosed with hemophilia have no other family members with the disorder. A doctor might check for hemophilia in a newborn if:
- Bleeding after circumcision of the penis goes on for a long time.
- Bleeding goes on for a long time after drawing blood and heel sticks (pricking the infant’s heel to draw blood for newborn screening tests).
- Bleeding in the head (scalp or brain) after a difficult delivery or after using special devices or instruments to help deliver the baby (e.g., vacuum or forceps).
- Unusual raised bruises or large numbers of bruises. If a child is not diagnosed with hemophilia during the newborn period, the family might notice unusual bruising once the child begins standing or crawling.
Haemophilia can be diagnosed before, during or after birth if there's a family history of the condition. Several options are available to parents.
If there's no family history of haemophilia, it's usually only diagnosed when a child begins to walk or crawl. They may experience joint bleeds or easy bruising. Mild haemophilia may only be discovered later, usually after an injury or a dental or surgical procedure.
Tests before pregnancy
Genetic testing and counselling are available to help determine the risk of passing the condition onto a child. This may involve testing a sample of your tissue or blood to look for signs of the genetic mutation that causes haemophilia.
Tests during pregnancy
If you become pregnant and have a history of haemophilia in your family, tests for the haemophilia gene can be carried out. These include:
- chorionic villus sampling (CVS) – a small sample of the placenta is removed from the womb and tested for the haemophilia gene, usually during weeks 11-14 of pregnancy
- amniocentesis – a sample of amniotic fluid is taken for testing, usually during weeks 15-20 of pregnancy
There's a small risk of these procedures causing problems such asmiscarriage or premature labour, so you may want to discuss this with the doctor in charge of your care.
Tests after birth
If haemophilia is suspected after your child has been born, a blood testcan usually confirm the diagnosis. Blood from the umbilical cord can be tested at birth if there's a family history of haemophilia. A blood test will also be able to identify whether your child has haemophilia A or B, and how severe it is.