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Updated: Aug 14, 2026
Measurement of Factor V Activity in Human Plasma Using a Microplate Coagulation Assay
Published on: September 9, 2012
von Willebrand factor ristocetin cofactor (VWF:RCo) assay: implementation on an automated coagulometer (ACL)
R Redaelli1, A R Corno, L Borroni
1Department of Hematology, Thrombosis and Hemostasis Unit, Ospedale Niguarda Ca' Granda, Milan, Italy. rosaria.redaelli@ospedaleniguardia.it
Background:
VWF:RCo assay is the standard and widely used laboratory test for von Willebrand disease (VWD) diagnosis. It is hampered by high intra- and inter-assay imprecision and is time consuming. Automation may improve the assay performance and allow its routine application.
Objective:
Automation of VWF:RCo on the ACL 7000 coagulometer (Instrumentation Laboratory, Milan, Italy) and its evaluation in VWD diagnosis.
Methods And Materials:
Method performance determination: precision, detection limit (DL), interferences, dose-response curve. Method comparison: analysis of 105 plasma samples from normal subjects (50), VWD type 1 (24), VWD type 2 (24) and VWD type 3 (7) with ACL VWF:RCo and comparison with the reference aggregometric (AGM) method.
Results:
ACL VWF:RCo: CVs around 10% vs. 19% of AGM method; DL: 0.08 U mL(-1); potential interferences from bilirubin, triglycerides and hemoglobin, avoided by suitable plasma dilution; high correlation with AGM VWF:RCo (Deming regression Y =-0.0277 + 1.0519X) either in normal or VWD plasmas. In VWD types 1 and 2, the VWF:RCo/VWF:Ag ratios are >0.6 or <0.6, respectively, when calculated with both AGM and ACL VWF:RCo values.
Conclusions:
The automated VWF:RCo on the ACL 7000 coagulometer shows precision improvement and high correlation with the reference AGM method. The test allows the diagnosis of both quantitative (VWD types 1 and 3) and qualitative (VWD type 2) forms of the disease. These results and the assay feasibility make it a suitable and reliable test for the routine diagnosis of VWD.
