An Automated pre-Dilution Setup for Von Willebrand Factor Activity Assays

Area of Science:

• Hematology
• Biotechnology
• Clinical Diagnostics

Background:

• Accurate quantification of von Willebrand factor ristocetin cofactor activity (VWF:RCo) is essential for diagnosing von Willebrand disease and assessing VWF concentrate quality.
• Current VWF:RCo assays, even on automated analyzers, exhibit significant intra- and inter-assay variation.
• Manual sample dilutions in VWF concentrate analysis are a primary source of imprecision and errors.

Purpose of the Study:

• To develop and validate a precise and accurate automated method for VWF:RCo determination.
• To reduce operator-dependent variability and improve standardization in VWF activity assays.
• To address the challenges of high manual dilutions for VWF concentrates.

Main Methods:

• An automated pre-dilution setup was integrated with a liquid handling system (CyBio FeliX).
• An adapted VWF:RCo assay was performed on a coagulation analyzer (BCS-XP).
• The automated method was compared against manual dilutions by an experienced operator across three analyzers.

Main Results:

• The automated method demonstrated comparable assay precision (CV = 5.9%) to manual dilutions (CV = 3.1%).
• No significant differences were observed between automated and expert manual VWF:RCo measurements.
• The automated procedure generated no outliers, unlike manual dilutions which had an 8.3% error rate.

Conclusions:

• The operator-independent, automated protocol standardizes VWF activity assays.
• This method provides an efficient and accurate way to fully automate VWF:RCo determination.
• The approach maintains the precision and accuracy of expert analysts, simplifying method transfer.