Ristocetin Cofactor Activity

Ristocetin Cofactor Activity measures how well a person's blood can help a protein called von Willebrand factor (vWF) work to form blood clots. In this test, a substance called ristocetin is used to activate vWF, prompting platelets (blood cells that help stop bleeding) to stick together. The activity level indicates the functionality of vWF—if it’s low, it may signal a bleeding disorder like von Willebrand disease. The test helps doctors evaluate the blood’s ability to form clots properly, guiding diagnosis and treatment for bleeding problems.