What is the quick laboratory test for von Willebrand disease (vWD)?

From the Guidelines

The most effective quick lab test for von Willebrand disease (vWD) is a combination of von Willebrand factor antigen (vWF:Ag), von Willebrand factor activity (vWF:RCo), and factor VIII activity, which should be ordered together as an initial screening panel, as recommended by the 2008 NHLBI/NIH guidelines 1. These tests are essential for the diagnosis of vWD, as they provide information on the amount and function of von Willebrand factor, as well as the activity of factor VIII, which is often reduced in vWD.

• The vWF:Ag measures the amount of von Willebrand factor protein present,
• while vWF:RCo assesses its functional ability to bind platelets,
• and factor VIII activity is included because vWF serves as a carrier protein for factor VIII. Additional helpful tests include a complete blood count to check for anemia and platelet count, and a PFA-100 closure time which can serve as a screening test for platelet function. It's important to note that these tests can be affected by various factors including stress, exercise, pregnancy, and certain medications, so proper patient preparation is essential, as stated in the guidelines 1. Testing should ideally be performed when the patient is not experiencing acute illness or stress, and multiple tests may be necessary for diagnosis as vWF levels can fluctuate, and specialized testing at reference laboratories may be required for definitive typing of vWD subtypes 1. The initial three VWD tests, including measurements of blood plasma VWF antigen (VWF:Ag), VWF ristocetin cofactor activity (VWF:RCo), and factor VIII coagulant activity (FVIII), are grade B recommendations and should be ordered together as an initial screening panel, as they may not only establish the diagnosis but also suggest the type and severity of VWD if it is present 1.

From the FDA Drug Label

Laboratory tests for assessing patient status include levels of factor VIII coagulant activity, factor VIII ristocetin cofactor activity, and factor VIII von Willebrand factor antigen. The skin bleeding time may be helpful in following these patients. The quick lab for von Willebrand disease includes:

• Factor VIII coagulant activity
• Factor VIII ristocetin cofactor activity
• Factor VIII von Willebrand factor antigen
• Skin bleeding time 2

From the Research

Laboratory Tests for von Willebrand Disease

The diagnosis of von Willebrand disease (VWD) involves a combination of clinical assessment and laboratory tests. The laboratory tests used to diagnose VWD include:

• VWF antigen (VWF:Ag) levels 3, 4, 5
• Ristocetin cofactor activity (VWF:RCo) 3, 6, 7, 5
• Collagen-binding activity (VWF:CB) 4, 5
• Factor VIII coagulant activity (FVIII:C) 3, 5
• VWF multimeric analysis 3, 4
• Ristocetin-induced platelet aggregation (RIPA) analysis 3, 5

Automated Assays for VWD Diagnosis

Automated assays have been developed to improve the reliability and efficiency of VWD diagnosis. These include:

• Automated VWF:RCo assay 7
• Fully automated chemiluminescent test panel including VWF:Ag, VWF:GPIbR, and VWF:CB assays 5
• Automated platelet function analysers such as the PFA-100 and the Xylum Clot Signature Analyser 3

Diagnostic Algorithms for VWD

Diagnostic algorithms have been developed to guide the diagnosis of VWD. These algorithms typically involve a combination of laboratory tests and clinical assessment. For example:

• The algorithm may start with first-level tests such as FVIII:C, VWF:Ag, and VWF:RCo, followed by second-level tests such as VWF:CB and VWF multimeric analysis 5
• The algorithm may also include the use of automated assays and platelet function analysers to improve the accuracy and efficiency of diagnosis 3, 7, 5

Limitations and Challenges of VWD Diagnosis

The diagnosis of VWD can be challenging due to the heterogeneity of the disease and the limitations of laboratory tests. For example:

• No single test is sufficient to diagnose all types of VWD 3
• The results of laboratory tests may be influenced by various factors such as blood sampling and processing, and the use of different assay methods 6, 7, 4
• The diagnosis of VWD may require a combination of laboratory tests and clinical assessment, and may involve the use of multiple diagnostic algorithms 3, 4, 5