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Von Willebrand Disease (VWD)
Part 2: NHLBI Diagnosis Guidelines

Laboratory Recommendations

VWD Diagnosis (Especially Type 1)

Slide 16

May 2011

What VWF reference values should be recommended for the "low cutoff?"

Persons with VWF values below 20 to 30 IU/dL have generally been found to have intragenic VWF mutations that strongly support VWD diagnosis, whereas above this level, other modifying factors may prominently influence VWF levels (such as ABO blood group – see next slides). The NHLBI VWD Guidelines expert panel conservatively recommended 30 IU/dL as the cutoff level for supporting the definite laboratory diagnosis of VWD – especially type 1 VWD (and in the absence of clearly supportive clinical assessment), for reasons discussed in the preceding slide (16). Other VWD experts, such as an Italian group, have suggested 40 IU/dL for such a cutoff value; and this recommendation is also supportable. A cutoff value of 50 IU/dL has been reported for type 1 VWD, in this Canadian study of children – when used in conjunction with clinical assessment including a bleeding history scoring tool. In summary, correlation of laboratory results with clinical information is indicated for improving VWD diagnosis and avoiding over-diagnosis and treatment.

VWD Diagnosis (Especially Type 1)


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