Ideally, testing is planned before the baby’s birth so that a blood sample can be drawn from the umbilical cord. Umbilical cord blood testing is better at discovering low levels of factor 8 than at finding low levels of factor 9, because factor 9 levels are not at a normal level until a baby is at least 6 months old.
Two types of tests are used for diagnosis: screening tests and clotting factor tests, which are also called factor assays.
Screening Tests
Screening tests are blood tests that reveal whether the blood is clotting properly. There are several types of screening tests for hemophilia:
Complete Blood Count (CBC) This test measures the amount of hemoglobin (the red pigment inside red blood cells that carries oxygen), the percentage of blood volume occupied by red blood cells (called the hematocrit), the size and amount of red blood cells, and the amounts of white blood cells and platelets in the blood. The CBC is normal in people with hemophilia, but if you have hemophilia and you have unusually heavy bleeding or bleed for a long period of time, the hemoglobin and the hematocrit can be low.
Activated Partial Thromboplastin Time (APTT) Test This test reveals how much time it takes for blood to clot; specifically, it measures the clotting ability of factors 8, 9, 11, and 12. If any of these clotting factors are diminished, it takes longer than normal for the blood to clot. The results of the APTT test will show a longer clotting time if you have hemophilia A or B.
Prothrombin Time (PT) Test This test also reveals how long it takes for blood to clot. It focuses on the clotting ability of factors 1, 2, 5, 7, and 10. If any of these factors are in short supply, it takes longer for the blood to clot. Most people with hemophilia A and B will have normal results on this test.
Fibrinogen Test This test also reveals how well a person can form a blood clot. Fibrinogen is also known as clotting factor 1.
Clotting Factor Tests
Clotting factor tests, which are required to diagnose a bleeding disorder, reveal the type of hemophilia and how severe it is. They check the levels of factor 8 or factor 9 in the blood, and show whether you have mild, moderate, or severe hemophilia.
How Hemophilia C Is Diagnosed
Hemophilia C can be diagnosed via genetic testing.
Prognosis of Hemophilia
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