By Connie Matthiessen
CONSUMER HEALTH INTERACTIVEBelow:
• How is hemophilia diagnosed?
• How is a woman diagnosed as a carrier?
• Are there women who are considered definite carriers, even in the absence of testing?
How is hemophilia diagnosed? Hemophilia is a rare type of bleeding disorder that occurs when there is a deficiency or absence of a particular protein (clotting factor) needed for blood to clot. As a result, a person with hemophilia will experience longer bleeding after an injury because the clot formed is not strong enough to stop the bleeding. There are thirteen clotting factors and they all work in sequence to help form a clot to reduce the flow of blood. Hemophilia is diagnosed through a blood test to measure levels of factor VIII or factor IX circulating in the blood. Factor VIII and factor IX levels are measured as a percentage. The average factor level in the population is 100 percent, but a level between 50 and 150 percent is considered to be normal. The type of clotting factor that is missing or lower than normal determines what kind of hemophilia you have. The two most common types are hemophilia A and hemophilia B. In hemophilia A, the missing clotting factor is factor VIII. Hemophilia A is sometimes referred to as classical hemophilia. In hemophilia B, the missing clotting factor is factor IX. How is a woman diagnosed as a carrier? There are two ways to test a woman to tell if she is a hemophilia carrier. A doctor may send a small amount of blood to the laboratory to measure circulating factor VIII or factor IX levels. Many women who carry the gene for hemophilia have lower than normal levels of clotting factor circulating in their blood. A doctor will examine the blood tests and the woman’s family history to help determine her chances of being a carrier. This type of testing cannot be done when a woman is pregnant or on taking birth control pills because these conditions can cause false readings. The second way to determine if a woman is a carrier is through DNA analysis. This type of testing is more accurate. A small sample of blood will be needed from the woman, from a family member who has hemophilia (the woman’s parents and other relatives). The blood is then sent to a special laboratory. The doctor will examine the results of the DNA analysis and the family tree in order to provide answers. Are there women who are considered definite carriers, even in the absence of testing? There are some women who are considered definite carriers and do not necessarily need to be tested. These women include: women who have fathers with hemophilia, mothers who have more than one son with hemophilia, or mothers who have one child with hemophilia and who have at least one other blood relative with the disorder. A woman with only one son who has hemophilia may or may not be a carrier because a genetic mutation could have occurred in the mother’s genes, or in one of her ancestors or in her son. If the mutation occurs on the son’s genes, the mother is not a carrier and her other children will not be affected with hemophilia. -- Connie Matthiessen is a freelance writer specializing in health issues. A former staff writer for the Center for Investigative Reporting, she served as an associate producer for a PBS series on health issues.
References
Hemophilia. National Heart, Lung, and Blood Institute, Disease and Conditions Index. www.nhlbi.nih/gov/health/dci/Diseases/hemophilia
Bleeding Disorders Info Center. Parents FAQs. National Hemophilia Foundation. Hemophilia.org
University of California at Children's Hospital. Hemophilia FAQ. 2003
Reviewed by Kim Schafer, a pediatric hemophilia nurse at the hematology/oncology division of the Department of Pediatrics at the University of California at Davis, a nationally recognized Hemophilia Treatment Center (HTC).
First published May 17, 2006
Last updated May 21, 2008
Copyright © 2006 Consumer Health Interactive
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