Haemophilia is a bleeding disorder that prevents blood from clotting normally. Understanding who should be tested and when testing should occur is crucial for early diagnosis and management. This article will outline the guidelines for Haemophilia Diagnosis, focusing on families with a history of the condition and individuals exhibiting signs or symptoms.
Who Should Be Tested for Haemophilia?
Identifying individuals who are at risk of haemophilia is the first step in diagnosis. Testing is particularly important in the following situations:
Families with a Known History of Haemophilia
A significant indicator for haemophilia testing is a family history of bleeding disorders. If there is a known history of excessive bleeding after injuries or surgeries, or unexplained deaths among male relatives (such as uncles, grandfathers, or cousins on the mother’s side), haemophilia should be considered. Consulting a doctor to discuss this family history is vital. Doctors often take a detailed family history to assess the likelihood of a bleeding disorder.
Newborns in families with a history of haemophilia, or whose mothers are known carriers, should be tested shortly after birth. Babies who exhibit bleeding symptoms at birth should also undergo immediate testing for haemophilia.
Umbilical cord blood tests are frequently used for newborn screening. However, it’s important to note that these tests are more effective at detecting low levels of factor VIII (associated with haemophilia A) than factor IX (associated with haemophilia B) in newborns. Factor IX levels develop more slowly and typically reach normal levels after six months of age. Therefore, a slightly low factor IX level at birth might not definitively indicate haemophilia B, and repeat testing may be necessary as the baby gets older. For a deeper understanding of inheritance patterns, resources on haemophilia inheritance are available.
Families with No Prior History of Haemophilia
It’s important to recognize that approximately one-third of babies diagnosed with haemophilia have no known family history of the disorder. In these cases, certain signs in newborns can prompt haemophilia diagnosis:
- Prolonged bleeding following circumcision.
- Extended bleeding after routine procedures such as blood draws or heel pricks for newborn screenings.
- Bleeding within the scalp or brain, particularly after a difficult delivery or one involving instruments like vacuum extractors or forceps.
- The appearance of unusual, raised bruises or an unexpectedly large number of bruises.
If haemophilia is not diagnosed in the newborn period, parents might notice unusual bruising as the child begins to crawl or stand. Severe haemophilia often presents with significant bleeding issues early in life and is frequently diagnosed within the first year. Milder forms of haemophilia may not be diagnosed until later in childhood or even adulthood, often after an injury or surgery reveals unexpected bleeding.
When is Haemophilia Diagnosis Performed?
For families with a history of haemophilia, testing is often requested for newborns soon after birth. However, diagnosis can occur at any age when bleeding symptoms become apparent or when risk factors are identified.
Types of Haemophilia Diagnostic Tests
Haemophilia diagnosis involves a combination of screening tests and clotting factor tests.
Screening Tests for Haemophilia
Screening tests are blood tests designed to assess whether blood is clotting correctly. These tests provide an initial indication of potential clotting problems. Common screening tests include:
Complete Blood Count (CBC)
A CBC measures various components of the blood, including haemoglobin levels, red blood cell characteristics, white blood cell counts, and platelet counts. In individuals with haemophilia, the CBC may often be normal. However, in cases of prolonged or severe bleeding, haemoglobin and red blood cell counts may be lower than normal due to blood loss.
Activated Partial Thromboplastin Time (APTT) Test
The APTT test measures the time it takes for blood to clot and evaluates the function of clotting factors VIII, IX, XI, and XII. If any of these factors are deficient, as in haemophilia A or B, the APTT result will show a prolonged clotting time.
Prothrombin Time (PT) Test
Similar to the APTT, the PT test also measures blood clotting time. It primarily assesses the function of clotting factors I, II, V, VII, and X. In most individuals with haemophilia A and B, the PT test results are typically normal because these forms of haemophilia primarily affect factors VIII and IX, which are more directly assessed by the APTT test.
Fibrinogen Test
This test measures the level of fibrinogen, also known as clotting factor I, which is essential for blood clot formation. A fibrinogen test may be ordered alongside other clotting tests or if a patient has abnormal results from PT or APTT tests, or both, to further investigate clotting ability.
Blood screening tests are vital in the haemophilia diagnosis process.
Clotting Factor Tests for Haemophilia
Clotting factor tests, also known as factor assays, are crucial for confirming a haemophilia diagnosis. These tests specifically measure the activity levels of factor VIII and factor IX in the blood. The results of these tests not only diagnose a bleeding disorder but also identify the specific type of haemophilia (A or B) and its severity. Determining the type and severity of haemophilia is essential for developing an effective and personalized treatment plan.
Haemophilia Severity Classification
The severity of haemophilia is classified based on baseline clotting factor activity levels, measured before any treatment is administered. This baseline level represents an individual’s inherent clotting ability.
Factor activity levels are reported as a percentage of a “normal” level, with the average normal level being 100% and the normal range typically between 50% and 150%. The International Society on Thrombosis and Haemostasis (ISTH) established the following severity categories in 2001 based on clotting factor levels:
| Severity | Levels of factor VIII or factor IX in the blood |
|---|---|
| Mild Haemophilia | Greater than 5% but less than 40% |
| Moderate Haemophilia | 1% to 5% |
| Severe Haemophilia | Less than 1% |
It is important to note that the 2001 ISTH classification didn’t specifically address individuals with clotting factor levels of 40% or greater. However, ISTH recommendations further define terms for women and girls carrying a haemophilia gene who have factor levels ≥40%: “symptomatic carrier” (with bleeding symptoms) and “asymptomatic carrier” (without bleeding symptoms). For those with factor levels <40%, the classifications of mild, moderate, and severe haemophilia apply.
Understanding haemophilia diagnosis, including who should be tested and the types of tests available, is critical for early detection and management of this bleeding disorder. Early diagnosis allows for timely interventions, improving the quality of life for individuals with haemophilia and their families.
