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Monitoring of von Willebrand Factor Inhibitors in Patients with Type 3 von Willebrand Disease Using a Quantitative Assay
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9 2021
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Source: Haemophilia. 27(5):823-829
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Details:
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Alternative Title:Haemophilia
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Personal Author:
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Description:Background:
Antibodies inhibiting von Willebrand factor (VWF) develop in a subset of patients with Type 3 von Willebrand disease (VWD3) and may be detected by their inhibition of ristocetin cofactor activity (VWF:RCo). Some also inhibit factor VIII activity (VIII:C).
Aim:
To describe monitoring of ten VWD3 patients for VWF inhibitors using a quantitative assay.
Methods:
VWF inhibitor was measured by comparing VWF:RCo activity of a mix of patient and pooled normal plasma (PNP) with a mix of buffer and PNP, using agglutination of fixed normal platelets in microtiter plates or lyophilized platelets in an aggregometer. VIII:C inhibitor was measured by Bethesda assay. Preanalytical heat treatment of patient plasma was used during treatment episodes.
Results:
Four of 10 patients monitored developed VWF inhibitors, 2 detected during bleeding episodes refractory to treatment and 2 on routine screening. Data from the first 5 patients were used to establish an arbitrary unit, VWU, defined as the amount of inhibitor per mL of patient plasma inactivating 25% of the activity of 1 mL of PNP. In 3 of 4 patients, both VWF:RCo and VIIII:C were inhibited at some time points, although VIII:C inhibition sometimes disappeared. In one patient, no VIII:C inhibition was seen. Two patients remained inhibitor positive more than 15 years after inhibitor detection, one became negative following immune tolerance induction, and one was deceased.
Conclusions:
VWF inhibitors can be quantitatively monitored in VWD3 patients. Preanalytical heat treatment may be required for their detection post infusion.
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Pubmed ID:34089550
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Pubmed Central ID:PMC8667261
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