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Von Willebrand Test

A set of reagents for determining von Willebrand factor activity in blood plasma (Von Willebrand Test) according to TU 9398-031-05595541-2010. It is designed for the quantitative determination of von Willebrand factor activity in blood plasma using both manual agglutination methods and optical aggregometers.

Von Willebrand factor circulates in the blood as a complex with coagulation factor VIII, facilitating the interaction of platelets with the damaged surface of blood vessels. A decrease in the content of this factor in blood plasma or its lack of biological activity is the main cause of von Willebrand disease. Therefore, determining its activity is one of the important diagnostic tests.

Von Willebrand disease is an inherited or acquired bleeding disorder resulting from qualitative or quantitative abnormalities of von Willebrand factor. Several types of von Willebrand disease are distinguished - Types 1, 2, and 3 with subtypes. Type 1 is the most common (70-80% of all cases), while Type 3 is the rarest (1-3%) and the most severe with a significantly pronounced bleeding syndrome, which is due to a deep reduction in both von Willebrand factor and factor VIII.

Method Principle: The method for determining von Willebrand factor activity is based on its ability to induce platelet agglutination in the presence of the antibiotic ristocetin. The ability to agglutinate is retained in platelets after their fixation with formaldehyde when the reaction to other aggregating inducers is completely lost.

In all dilutions of the calibrator plasma, von Willebrand factor activity is determined. On the X-axis on a logarithmic scale, von Willebrand factor activity is plotted in%, and on the Y-axis, the time of agglutinate formation in seconds. Using the calibration graph and the value of the agglutinate formation time in the test sample, von Willebrand factor activity in% is determined.

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"Von Willebrand Test Kit" composition:

  • Fixed human platelets – 2 vials;
  • Ristomycin (8mg/vial) – 2 vials;
  • Plasma calibrator (1 ml/vial) – 1 vial;
  • Buffer concentrate (5 ml/vial) – 1 vial.

One kit is intended for conducting 40 analyses on an aggregometer with a consumption of 0.05 ml of ristomycin per analysis or 40 manual analyses with a consumption of 0.05 ml of a mixture of fixed platelets with ristomycin per analysis.

In the normal state, von Willebrand factor activity is 70–130%.

A result less than 40% von Willebrand factor activity indicates von Willebrand disease. An exception is Type 2B von Willebrand disease, which is characterized by an increase in platelet aggregation by 1.5-2 times when using ristomycin at a low concentration as an inducer.

Complete diagnosis and determination of von Willebrand disease require additional research.

Normal and pathological values of von Willebrand factor activity should be controlled using Control Plasma, code KM-2.