Diagnosing hemophilia involves a series of blood tests that check the activity of various clotting factors in your blood.
Hemophilia is a rare bleeding disorder that prevents your blood from clotting correctly. It happens due to a lack of special proteins in your blood called clotting factors.
Hemophilia is relatively rare and typically runs in families, mainly affecting people assigned male at birth. The Centers for Disease Control and Prevention (CDC) estimates that around 33,000 males in the United States have hemophilia.
If a doctor suspects that you have hemophilia, several lab tests can help confirm the diagnosis. Most tests to diagnose this condition require a blood draw.
This procedure is safe and generally only involves minor discomfort from the needle. In rare cases, your vein may become inflamed and swollen at the puncture site. However, note that hemophilia may also cause you to have prolonged bleeding after the blood draw.
This article will take you through the various tests that doctors use to diagnose hemophilia.
Clotting factor tests
Clotting factor tests, also known as factor assays , are the main tests that doctors use to diagnose hemophilia . They test for the presence of various clotting factors , which are proteins that help your blood clot.
Deficiency in clotting factor VIII causes a common type of hemophilia known as hemophilia A . Lack of clotting factor IX, on the other hand, causes hemophilia B . Other types of hemophilia are less common.
Clotting factor tests measure the levels of clotting factors VIII and IX in your blood. These tests can also determine the severity of hemophilia.
| Hemophilia A or B severity | Levels of clotting factors VIII or IX in the blood |
|---|
| mild | 6% to 40% |
| moderate | 1% to 5% |
| severe | less than 1% |
Complete blood count
A complete blood count (CBC) is a standard test that measures different components of your blood, including:
The CBC provides a broad picture of your overall blood health. It can detect anemia , which can affect people who have frequent bleeding episodes. It can also detect infections and other blood disorders that may make hemophilia worse.
Activated partial thromboplastin time (APTT) test
The activated partial thromboplastin time (APTT) test evaluates how long it takes your blood to clot. Doctors often use it to detect bleeding disorders , including hemophilia.
To perform this test, a doctor will mix your blood with chemicals that trigger clotting. The lab then measures the time it takes for your blood to clot.
The typical range for clotting times on an APTT test is 25 to 35 seconds . Longer-than-usual clotting times can indicate hemophilia or another clotting disorder.
Prothrombin time (PT) test
The prothrombin time (PT) test is another test that measures how long it takes for your blood to clot.
It has a similar procedure to the APTT test, but it uses different chemicals to measure clotting times. It also checks the activity of different clotting factors. Since it doesn’t test for factors VIII and IX, people with hemophilia A or B will have a typical PT test result of 10 to 13 seconds .
Healthcare professionals may also use a value called the international normalized ratio (INR) , which expresses your PT result compared with a standard control. An INR of 1.0 means that your test and the control test have the same time. A typical INR is 0.8 to 1.2 .
PT and APTT testing in hemophilia
Doctors usually order the APTT and PT tests together because they measure the activity of different clotting factors .
| PT test measures | APTT test measures |
|---|
• factor I
• factor II
• factor V
• factor VII
• factor X | • factor VIII
• factor IX
• factor XI
• factor XII |
Fibrinogen test
Fibrinogen is another name for clotting factor I. Similar to other factor assays, this test measures the level of factor I in your blood.
Healthy plasma fibrinogen levels range from 200 to 400 milligrams per deciliter (2 to 4 grams per liter). Low levels indicate a clotting disorder called fibrinogen deficiency.
Genetic testing
Genetic testing can confirm a hemophilia A or B diagnosis by identifying mutations in the genes responsible for producing clotting factors VIII or IX.
As with other hemophilia tests, genetic testing typically involves a blood draw. A doctor will then send your sample to a lab for a DNA analysis.
Genetic testing can also determine if you’re a carrier of a hemophilia mutation, meaning that you don’t have hemophilia but can pass it down to your children. This may be important for family planning.
Genetic testing is typical for people who have a family history of hemophilia. For the most accurate genetic test, a relative assigned male at birth who has hemophilia should also have a genetic test to detect the exact mutation responsible for hemophilia in your family.
Takeaway
Diagnosing hemophilia involves a series of blood tests that measure the levels of clotting factors in your blood, evaluate blood clotting times, and detect the mutations responsible for this condition. Each test provides valuable information to help healthcare professionals make an accurate diagnosis.
Blood tests can sometimes be unnerving. But understanding the procedures, what they measure, and how to interpret the results can help you feel more prepared and in control. Always discuss your concerns and results with your doctor to ensure that you receive the best possible care.
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