Hemophilia is a bleeding disorder in which blood clotting is impaired. Although the bleeding symptoms are similar in hemophilia A and B, the underlying causes are different — a deficiency of factor VIII in hemophilia A and factor IX in hemophilia B. Therefore, it’s important to diagnose the type of hemophilia to decide on the appropriate therapy.
If a patient has a bleeding problem, a physician first inquires about the medical history of the family. Hemophilia testing is essential for the optimal management of hemophilia. It includes a physical exam, blood screening tests, and clotting factor tests. The blood screening tests are necessary to determine the delay in blood clot formation. Clotting factor tests, also called factor assays, are required to determine the levels of clotting factors. The results of these tests reveal the type and severity of hemophilia.
Family history of bleeding disorder
If there is a family history of excessive bleeding following an injury or surgery, it must be discussed with the doctor to identify the possibility of hemophilia. People with a family history may get their male newborns tested. It would be best to test for hemophilia by drawing blood from the umbilical cord immediately after birth to determine the level of clotting factors in the blood.
Umbilical cord blood testing is better at finding low levels of factor VIII because factor IX reaches its normal levels when babies are six months old. Therefore, low levels of factor IX at birth do not necessarily indicate hemophilia B.
No family history of bleeding disorder
About one-third of hemophilia patients have no family history of the disease. The doctor may test for hemophilia in a newborn if there is prolonged bleeding after circumcision, blood withdrawal, or delivery. In babies with hemophilia who have not been diagnosed at birth, unusual bruising may be observed during crawling. Severe hemophilia in babies is diagnosed early due to serious bleeding problems. But mild hemophilia may not be diagnosed until adulthood.
Hemophilia screening tests
Blood tests that are used to determine if the blood is clotting properly are called screening tests. Types of screening tests are complete blood count (CBC), activated partial thromboplastin time (APTT) test, prothrombin time (PT) test, and fibrinogen test.
Complete blood count (CBC)
This test measures the amount of hemoglobin (the red pigment that carries oxygen within the red blood cells), the size and number of red blood cells (RBCs), and the number of white blood cells and platelets in the blood. CBC results are normal in people with hemophilia, but there is a decrease in hemoglobin and RBCs in the case of heavy or prolonged bleeding.
Activated partial thromboplastin time (APTT) test
This test measures the delay in blood clot formation and the clotting ability of factors VIII, IX, XI and XII. If any of the clotting factors are too low, it takes longer for the blood to clot. Patients with hemophilia A or hemophilia B show a longer clotting time in this test.
Prothrombin time (PT) test
This test also measures the time it takes for the blood clot to form. It measures the clotting ability of factors I, II, V, VII, and X. 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 for patients with hemophilia A or hemophilia B since these conditions are caused by defects in factors VIII and IX, respectively.
Fibrinogen (also known as clotting factor I) test assesses the patient’s ability to form a blood clot. This test is performed along with other blood clotting tests or when a patient has an abnormal PT or APTT test result.
Clotting factor tests
Clotting factor tests, also called factor assays, are needed to diagnose a bleeding disorder. This blood test is used to identify the type and severity of hemophilia, which is important to create the best treatment plan.
Depending on the levels of clotting factors VIII or IX, hemophilia A and B are classified as mild, moderate or severe. The level of clotting factor is between 50 and 100 percent in healthy people, but it is between 5 and 50 percent in people with mild hemophilia, between 1 and 5 percent in people with moderate hemophilia, and at less than 1 percent in people with severe hemophilia.
The severity of symptoms may sometimes overlap between the categories. For example, patients with mild hemophilia may have bleeding problems similar to those with moderate hemophilia.
Female hemophilia carriers can undergo “preimplantation diagnosis” to ensure they do not pass the disease onto their children. Preimplantation diagnosis can only be performed in conjunction with IVF treatment. For this, the eggs of a female carrier are fertilized by the sperm of the father in the laboratory. The resulting embryos are genetically tested and only those that do not have the faulty hemophilia gene are implanted in the womb.
Prenatal testing for hemophilia
A pregnant hemophilia carrier can get the disorder diagnosed in their unborn baby as early as 12 weeks into their pregnancy. Prenatal diagnosis can be done at nine to 11 weeks by chorionic villus sampling (CVS) or by fetal blood sampling at a later stage (18 weeks or more).
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