From the Guidelines
The FVIII:vWF ratio is a critical diagnostic tool, and a ratio of >0.5-0.7 is generally considered normal, while a ratio of <0.5-0.7 may indicate Type 2 VWD variants, as suggested by the 2008 NHLBI/NIH guidelines 1. When evaluating the FVIII:vWF ratio, it's essential to consider the different types of von Willebrand disease (VWD) and their characteristic laboratory values.
- Type 1 VWD is characterized by a partial quantitative VWF deficiency, with a VWF:RCo/VWF:Ag ratio of >0.5-0.7 1.
- Type 2 VWD variants, including 2A, 2B, and 2M, typically have a VWF:RCo/VWF:Ag ratio of <0.5-0.7, indicating a decrease in VWF-dependent platelet adhesion 1.
- Type 2N VWD is marked by a markedly decreased VWF binding affinity for FVIII, resulting in a VWF:RCo/VWF:Ag ratio of >0.5-0.7, often with significantly decreased FVIII levels 1.
- Type 3 VWD is characterized by a virtually complete deficiency of VWF, with very low VWF:RCo and VWF:Ag levels, and a significantly decreased FVIII level 1. It's crucial to interpret the FVIII:vWF ratio in the context of the patient's clinical presentation, medical history, and other laboratory results to ensure an accurate diagnosis and appropriate treatment plan.
- The test should be performed when the patient is in a stable condition, as both FVIII and vWF are acute phase reactants that can be elevated during stress, inflammation, or pregnancy 1.
- Laboratory testing should include both quantitative (FVIII and vWF antigen levels) and qualitative (vWF activity) assessments to properly evaluate the ratio and determine the appropriate diagnosis and treatment plan 1.
From the Research
FVIII:VWF Ratio
- The FVIII:VWF ratio is an important consideration in the treatment of von Willebrand disease (VWD) 2, 3, 4, 5, 6.
- Studies have shown that varying amounts and quality of VWF and FVIII in plasma-derived concentrates can contribute to the lack of a standardized approach to replacement therapy 2.
- The treatment of VWD has undergone a change from plasma-derived VWF/FVIII concentrates with VWF:ristocetin cofactor (RCo)/FVIII ratios ≤1, to those with VWF:RCo/FVIII ratios >10, to a recombinant VWF 2.
- FVIII/VWF concentrates with a high content of FVIII/VWF have been shown to be effective in the treatment of VWD, with excellent to good clinical efficacy in 92% of bleeding episodes and in 93% of surgical procedures 3.
- The dosage and timing of FVIII/VWF administration should be planned to keep FVIII:C concentrations between 50 U/dl and 150 U/dl in the postoperative period to minimize the risk of thrombotic events 4.
- Dosing of VWF/FVIII concentrates can be calculated based on the FVIII content or VWF functional activity, such as VWF ristocetin cofactor activity (VWF:RCo) 5.
- The correct use of FVIII/VWF concentrates in VWD and hemophilia A (HA) has been reported in several national and international guidelines 6.