Knowledge Check

What color top tube is blood collect in for PT and aPTT?

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Blue top

What anticoagulant does the blue top tube contain?

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Sodium citrate

What is the differential diagnosis for an isolated elevation of aPTT?

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Deficiency of, or inhibitor against, FXII, FXI, FIX, and/or FVIII

Name the more common medical conditions associated with AVWS

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Lymphoproliferative disorders
Myeloproliferative neoplasms
Cardiac conditions
Autoimmune disorders

AVWS, acquired von Willebrand syndrome

Name 4 mechanisms of reduced VWF activity in AVWS

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Antibody-mediated clearance or inhibition of function
Shear stress-induced proteolysis
Adsorption onto cells
Decreased synthesis

What are three screening tests for VWD?

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VWF:Ag
VWF:RCo
(FVIII often included)

VWD, von Willebrand disease

What proportion of AVWS cases are associated with reduced high molecular weight vWF multimers?

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About 1/3

AVWS, acquired von Willebrand syndrome; vWF, von Willebrand factor

Should you test for autoantibodies against VWF in cases of suspected AVWS?

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No, they are rarely positive even if an antibody is present

AVWS, acquired von Willebrand syndrome; vWF, von Willebrand factor

What does it mean when the vWF:RCo is disproportionately reduced relative to vWF:Ag?

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Suggests type 2A VWF from increased clearance of high molecular weight VWF multimers

Why is the aPTT elevated in AVWS?

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Because reduced levels of VWF lead to lower levels of FVIII

AVWS, acquired von Willebrand syndrome

What are the 2 pillars in treatment of AVWS?

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Treat active bleeding
Treat underlying medical condition

AVWS, acquired von Willebrand syndrome

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