What does an elevated Ristocetin cofactor result indicate in von Willebrand disease?

From the Guidelines

An elevated Ristocetin cofactor result indicates normal or increased von Willebrand factor (VWF) activity in von Willebrand disease (VWD) patients, as it measures the ability of VWF to bind to platelets in the presence of ristocetin 1.

Key Points

• The VWF:RCo assay is used to measure VWF activity, which is essential for platelet adhesion and blood clotting 1.
• An elevated VWF:RCo result is typically seen in Type 2N VWD, where the VWF binding affinity for FVIII is markedly decreased, but the VWF:RCo/VWF:Ag ratio is usually >0.5–0.7 1.
• However, it's essential to consider the VWF:RCo/VWF:Ag ratio, as a ratio <0.5–0.7 may indicate Type 2A, 2B, or 2M VWD, despite a normal or elevated VWF:RCo result 1.
• The VWF:RCo assay has limitations, including poor sensitivity and potential for false diagnoses due to instability and batch-to-batch variability of reagents 1.
• Patient-related factors, such as stress, exercise, and inflammation, can also affect VWF levels and VWF:RCo results 1.

Laboratory Considerations

• VWF:RCo results should be interpreted in conjunction with VWF:Ag and FVIII levels, as well as clinical information, to determine the type and severity of VWD 1.
• The NHLBI VWD Guidelines recommend using a combination of VWF:Ag, VWF:RCo, and FVIII assays for initial evaluation, with reflexive testing or specialized assays (e.g., multimer analysis) as needed 1.

From the Research

Elevated Ristocetin Cofactor Result in von Willebrand Disease

• An elevated Ristocetin cofactor result is not typically indicative of von Willebrand disease, as the disease is usually characterized by a deficiency or dysfunction of von Willebrand factor (VWF) 2, 3, 4.
• The Ristocetin cofactor activity assay is used to measure the ability of VWF to bind to platelets in the presence of Ristocetin, and is an important diagnostic tool for von Willebrand disease 2, 5, 6.
• Elevated Ristocetin cofactor activity may be seen in some cases, but this is not typically considered a diagnostic criterion for von Willebrand disease 3.
• The diagnosis of von Willebrand disease is typically based on a combination of clinical and laboratory findings, including low VWF antigen levels, low VWF activity, and abnormal VWF multimer patterns 3, 4, 5, 6.
• It is worth noting that there are different types of von Willebrand disease, and the laboratory findings can vary depending on the specific type and severity of the disease 3, 5, 6.