Classification of Hemophilia A with 4% Factor VIII Activity
A patient with hemophilia A containing 4% VIII:C activity is classified as moderate hemophilia. 1, 2
Classification System for Hemophilia A
According to the International Society on Thrombosis and Haemostasis (ISTH) guidelines, hemophilia A severity is classified based on plasma levels of factor VIII (FVIII) activity as follows:
- Severe: <1% factor VIII activity
- Moderate: 1-5% factor VIII activity
- Mild: >5-40% factor VIII activity 1, 2
Since this patient has a factor VIII coagulant (VIII:C) activity of 4%, they fall within the moderate hemophilia A category. This classification has been well-established and correlates well with clinical profiles in most cases, as confirmed by the ISTH Project Group 1.
Clinical Implications of Moderate Hemophilia
Patients with moderate hemophilia A (1-5% factor VIII activity) typically experience:
- Milder spontaneous bleeding episodes compared to severe hemophilia
- Traumatic bleeds
- Less frequent joint damage than severe hemophilia
- Potential need for prophylactic therapy depending on bleeding phenotype 2, 3
Important Considerations
- While classification is based on factor VIII levels, it's important to recognize that there can be clinical heterogeneity in bleeding patterns among patients with the same factor VIII levels 1, 3
- The chromogenic factor VIII assay may provide more accurate results in some cases, particularly for mild hemophilia diagnosis, as it better reflects the severity status than the one-stage assay 4
- Some patients may have discrepancies between laboratory classification and clinical bleeding phenotype due to various factors including:
Treatment Approach for Moderate Hemophilia A
For patients with moderate hemophilia A (4% factor VIII activity):
- Factor VIII concentrates may be needed for bleeding episodes or before procedures
- Dosing based on: Weight (kg) × desired FVIII increase (%) × 0.5 = units required 2
- Some patients with moderate hemophilia may benefit from prophylactic therapy depending on their bleeding phenotype 2
- Regular monitoring of factor VIII levels and screening for inhibitor development is essential 2
The classification system provides a framework for treatment decisions, but the actual bleeding phenotype should always be considered when determining the optimal management approach for patients with hemophilia A.