A rare blood disorder largely inherited through genetics, hemophilia inhibits the body’s ability to clot blood. Due to a lack of clotting factors (or clotting proteins), patients may experience unwarranted or prolonged bleeding, both internal and external.
Hemophilia is diagnosed through blood tests that analyze the level of clotting factors in the blood, as well as by reviewing the medical histories of both the patient and their family.
Since the vast majority of patients are genetically predisposed to the condition, hemophilia can be diagnosed very early. Given the higher rate of diagnoses in males, tests are more common among younger boys, and a review of their family medical history will often focus on male relatives. Looking at the immediate family’s medical history, however, does not always provide clues as to the root of a patient’s hemophilia, as approximately one-third of patients report no close relatives having the disorder.
Those at genetic risk for hemophilia are often asked by their doctor to undergo a complete blood count (CBC) test, which measures hemoglobin levels. Low levels of hemoglobin—which are the molecule that carries oxygen from the lungs—can be an indicator of hemophilia. CBCs also test for red blood levels, with low levels being another possible explanation for symptoms like prolonged bleeding.
CBC tests indicating the possibility of hemophilia may prompt a doctor to administer an Activated Partial Thromboplastin Time Test (APTT) and a Prothrombin Time Test (PT), analyzing the duration of time it takes for blood to clot, as well as various clotting factors. A long clotting time is a strong sign of hemophilia.
If hemophilia is diagnosed, specific clotting factor tests are administered to determine the type and severity of the disorder. Hemophilia typically varies in severity from mild to moderate to severe. Mild hemophilia corresponds to 6-49% clotting factor levels; moderate hemophilia involves 1-5% clotting factor levels; severe hemophilia—the most common form—involves less than one percent clotting factor levels.
Innovations in diagnostic screening now include prenatal testing and are able to detect certain abnormalities indicative of hemophilia in a fetus after the 11th week of pregnancy. Further testing for may be done after 18 weeks, involving blood samples that evaluate clotting factor levels. Given the invasive nature of these tests, though, doctors often only recommend them if the fetus is male with a family medical history of the disorder.
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