Samples for any coagulation tests must be filled to the black fill line indicated on the sample tube. Any sample filled above or below this level will be rejected and a repeat sample will be required
Note: For external requests please click Here for Coagulation Disorders request form. Please complete all information fully
Samples that meet the following criteria will not be processed:
- Haemolysed, clotted, underfilled or overfilled samples.
- Samples >12 hours old from the time of collection.
- Samples received from other hospital laboratories that have been frozen and thawed.
- Samples which fail the minimum data set.
VWF:Ag and VWF:RCo:
- VWF results may be affected by bilirubin above 14mg/dl and triglycerides above 1500mg/dl.
- The presence of Rheumatoid factor may produce and overestimation of the test result.
- VWF is an acute phase protein and may be elevated above baseline in a variety of conditions including inflammation, stress, exercise, liver disease, pregnancy or oestrogen therapy. These conditions may obscure diagnosis of the milder forms of von Willebrand disease (vWD). Repeat testing may be indicated.
- Lipaemic samples may lead to an underestimation of the VWF:RCo result.
- vWF:CBA levels vary considerably in any individual. They can be falsely elevated due to many reasons such as stress, exercise, smoking, pregnancy, oral contraception, infection and chronic liver disease. It is important to have the patient relaxed before taking samples for this assay and also to be aware of their clinical circumstances for correct interpretation of results.
- Reduced levels of vWF:CBA are associated with blood group O.
Factor VIII 57-158 u/dL
von Willebrand Factor Antigen (VWF:Ag) 48-175 u/dL
von Willebrand Factor Activity (VWF:RCo, RICOF) 47-154 u/dL
von Willebrand Factor Collagen Binding activity (vWF:CBA) 42-259 u/dL