Hemophilia laboratory findings: Difference between revisions
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{{Hemophilia}} | {{Hemophilia}} | ||
==Screening Tests== | {{CMG}};{{AE}} {{Simrat}} | ||
==Overview== | |||
Laboratory findings consistent with the diagnosis of hemophilia include unaffected prothrombin time, prolonged partial thromboplastin time, unaffected bleeding time and unaffected platelet count. | |||
==Screening Tests== | |||
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: | *You or your child also will likely have a physical exam and blood tests to diagnose hemophilia. Blood tests are used to find out: | ||
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Simrat Sarai, M.D. [2]
Overview
Laboratory findings consistent with the diagnosis of hemophilia include unaffected prothrombin time, prolonged partial thromboplastin time, unaffected bleeding time and unaffected platelet count.
Screening Tests
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.
Screening tests are blood tests that show if the blood is clotting properly. Types of screening tests:
Complete Blood Count (CBC)
This common test measures the amount of hemoglobin (the red pigment inside red blood cells that carries oxygen), the size and number of red blood cells and numbers of different types of white blood cells and platelets found in blood. The CBC is normal in people with hemophilia. However, if a person with hemophilia has unusually heavy bleeding or bleeds for a long time, the hemoglobin and the red blood cell count can be low.
Activated Partial Thromboplastin Time (APTT) Test
This test measures how long it takes for blood to clot. It measures the clotting ability of factors VIII (8), IX (9), XI (11), and XII (12). If any of these clotting factors are too low, it takes longer than normal for the blood to clot. The results of this test will show a longer clotting time among people with hemophilia A or B.
Prothrombin Time (PT) Test
This test also measures the time it takes for blood to clot. It measures primarily the clotting ability of factors I (1), II (2), V (5), VII (7), and X (10). If any of these factors are too low, it takes longer than normal for the blood to clot. The results of this test will be normal among most people with hemophilia A and B.
Fibrinogen Test
This test also helps doctors assess a patient’s ability to form a blood clot. This test is ordered either along with other blood clotting tests or when a patient has an abnormal PT or APTT test result, or both. Fibrinogen is another name for clotting factor I (1).
Clotting Factor Tests
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. It is important to know the type and severity in order to create the best treatment plan.
| Condition | Prothrombin time | Partial Thromboplastin Time | Bleeding Time | Platelet Count |
|---|---|---|---|---|
| Heamophilia A or B | Unaffected | Prolonged | Unaffected | Unaffected |
| Von Willebrand Disease | Unaffected | Prolonged or Unaffected | Prolonged | Unaffected |
| Thrombocytopenia | Unaffected | Unaffected | Prolonged | Decreased |
| Adapted from Wikipedia hemophilia Laboratory Finding> "Wikipedia Hemophilia Laboratory Finding". | ||||
The test results will show whether you have hemophilia, what type of hemophilia you have, and how severe it is. Hemophilia A and B are classified as mild, moderate, or severe, depending on the amount of clotting factor VIII or IX in the blood. The severity of symptoms can overlap between the categories. For example, some people who have mild hemophilia may have bleeding problems almost as often or as severe as some people who have moderate hemophilia. Severe hemophilia can cause serious bleeding problems in babies. Thus, children who have severe hemophilia usually are diagnosed during the first year of life. People who have milder forms of hemophilia may not be diagnosed until they're adults.
| Severity | Levels of Factor VIII (8)
or IX (9) in the blood |
|---|---|
| Normal (person who does not have hemophilia) | 50% to 100% |
| Mild hemophilia | Greater than 5% but less than 50% |
| Moderate hemophilia | 1% to 5% |
| Severe hemophilia | Less than 1% |
| Adapted from CDC Hemophilia Diagnosis> "CDC Hemophilia Diagnosis". | |
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