From the Guidelines
Laboratory tests for diagnosing and managing hemophilia should include coagulation screening tests, such as a complete blood count (CBC), prothrombin time (PT), activated partial thromboplastin time (aPTT), and thrombin time (TT), as well as specific factor assays, including Factor VIII activity for hemophilia A and Factor IX activity for hemophilia B, using assays such as the OSCA and CHR, as recommended by recent studies 1.
Initial Testing
Initial testing should consist of:
- Complete blood count (CBC)
- Prothrombin time (PT)
- Activated partial thromboplastin time (aPTT)
- Thrombin time (TT) In hemophilia, the aPTT is typically prolonged while other screening tests remain normal.
Factor Assays
Specific factor assays are essential for diagnosis, particularly:
- Factor VIII activity for hemophilia A
- Factor IX activity for hemophilia B Levels below 40% indicate hemophilia, with severity classified based on factor levels:
- Severe (<1%)
- Moderate (1-5%)
- Mild (5-40%)
Ongoing Management
For ongoing management, regular factor level monitoring is necessary to guide replacement therapy, using assays such as the OSCA and CHR, which are recommended to be made widely available in coagulation laboratories and licensed for use globally 1. Additional tests include:
- Inhibitor screening using the Bethesda assay, performed regularly, especially after initial treatment and before invasive procedures
- Genetic testing to identify specific mutations, valuable for family counseling and predicting disease severity
- Liver function tests when using factor concentrates
- Assessment of viral markers to monitor for potential transfusion-transmitted infections
These tests collectively enable accurate diagnosis, appropriate treatment planning, and effective long-term management of hemophilia, as emphasized by recent recommendations for practice 1.
From the FDA Drug Label
Hemophilia A Prior to treatment with desmopressin acetate injection, verify that factor VIII coagulant activity levels are >5% and exclude the presence of factor VIII autoantibodies. Also assess serum sodium and aPTT prior to treatment
To diagnose and manage hemophilia, the following laboratory tests should be ordered:
- Factor VIII coagulant activity levels to verify levels are >5%
- Factor VIII autoantibodies to exclude their presence
- Serum sodium to assess sodium levels prior to treatment
- aPTT (activated Partial Thromboplastin Time) to assess prior to treatment These tests are necessary to ensure safe and effective treatment with desmopressin acetate injection 2 2.
From the Research
Laboratory Tests for Hemophilia
To diagnose and manage hemophilia, several laboratory tests are essential. These tests help confirm the diagnosis, determine the severity of the condition, and guide treatment decisions. The key laboratory tests for hemophilia include:
- Factor VIII (FVIII) activity assay for hemophilia A 3
- Factor IX (FIX) activity assay for hemophilia B 3
- Activated partial thromboplastin time (aPTT) 4
- Bethesda assay to measure inhibitor potency 5
- Chromogenic assays for FVIII and FIX activity 4
Special Considerations
When interpreting laboratory results for hemophilia, it's crucial to consider the potential limitations and challenges associated with certain assays. For example:
- Interference from anticoagulants or lupus anticoagulant can affect assay results 5
- The Bethesda assay may not provide an exact quantification of inhibitor potency due to the non-log-linear relationship between inhibitor concentration and effect on residual FVIII:C activity 5
- Extended half-life (EHL) recombinant clotting factors and non-factor replacement therapeutics can pose challenges to coagulation laboratories due to the lack of standardized assays 4
Diagnostic Approach
A stepwise approach to laboratory diagnosis is recommended, taking into account the patient's clinical history and the potential limitations of certain assays 4. This approach may involve:
- Initial screening with aPTT and FVIII or FIX activity assays
- Confirmation of diagnosis with additional assays, such as chromogenic assays or the Bethesda assay
- Regular monitoring of hemostatic parameters to guide treatment decisions and adjust therapy as needed 4