Specimen Requirements

Minimum Specimen Requirements

Stability

Days Performed

Varies

Turnaround Time

8 - 9 days

Methodology

Special Info

This test is New York DOH approved.

Clinical Info

von Willebrand disease (VWD) is a bleeding disorder characterized by either quantitative or qualitative defects of von Willebrand factor (VWF). Accurate measurement of VWF activity by assessment of its interaction with platelets is an essential component of the evaluation of a patient where there is concern for von Willebrand disease. While the VWF Ristocetin Cofactor Activity (VWF: RCo) assay has been used for decades to measure VWF platelet binding activity, the assay’s imprecision and poor sensitivity are significant drawbacks. The VWF GPIbM Activity assay measures binding of VWF to mutant GPIb-alpha without the need for ristocetin and is well correlated with the VWF:RCo assay. The VWF GPIbM Activity assay demonstrates superior precision and sensitivity compared with the VWF ristocetin cofactor assay. Furthermore, it is not subject to falsely low values seen in individuals who possess the common p.D1472H polymorphism or the rare p.P1467S variant, both of which confound the accurate diagnosis of von Willebrand disease. Since discrepancies between VWF activity and VWF antigen suggest variant VWD, accurate measurement of VWF activity via the VWF GPIbM Activity assay offers an advance in the evaluation of patients where there is concern for VWD.

Clinical Limitation

VWF is an acute phase reactant. Levels will be elevated postoperatively, with inflammation, stress, physical activity, pregnancy, estrogen therapy and hyperthyroidism. VWF levels may be artifactually reduced as a consequence of improper sample handling. VWF activity assays should be correlated with other VWF assays and with patient clinical history to support an appropriate diagnosis. For some cases of type 2B VWD, VWF GPIbM Activity will report a higher activity level than VWF Ristocetin Cofactor Activity. Therefore, VWF GPIbM Activity results should be interpreted cautiously when monitoring perioperative therapy in patients with type 2B VWD.