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Test Code: F8Stud Preferred Name von Willebrand disease screen

No
3 hours, phone request only
Weekly
1 week
Medicare Item

Test Tubes

ImageSpecimen TypeSpecimen VolumeTube Type
Blood (adult)2.7mL x 3Sodium Citrate 2.7 mL (Solid Pale Blue Top)
Blood (paediatric)1.8 mL x 2Sodium Citrate 1.8 mL Paed (Clear/Pale Blue Inner)
Whole Blood3mLEDTA 3 mL whole blood (Lavender top)
Whole blood500 uL x 1EDTA 500 uL Microtainer (Lavender Top)

COLLECTION NOTES

Note: Please number the Na Citrate tubes in order of their collection.
A minimum collection of 1.8 mL Na Citrate is required - if difficulty collecting this amount please contact laboratory.
If  PFA or platelet aggregation studies are also requested, do not collect 1.0 ml sodium citrate tubes.
An EDTA specimen for platelet count must also be collected.
Specimens must be stored at room temperature and transported to Laboratory in a red bag ASAP. Maximum delay to testing laboratory must not exceed 2 hrs.

GENERAL NOTES



Factor 8 studies is a combination of tests including Factor VIII, Von Willebrand Testing, Coagulation profile and Full Blood Count.

von Willebrands Disease screen includes Factor VIII (vWF:FVIIIC), von Willebrands factor (VWF:Ag) and Ristocetin Co Factor activity (vWF:RCo).  If results indicate VWD, Collagen Binding Assay (vWF:CBA) and Multimer analysis (vWF:Multimer) maybe added if frozen plasma is available. If von Willebrands Disease screen is urgent please notify Haematology laboratory (ext: 1672).

A Blood group should also be performed, as different levels of von Willebrands factor have been demonstrated in different blood groups (lowest in O Group patients). von Willebrand levels are lower in the follicular phase of the menstrual cycle (the test should ideally be performed then) and may be reduced in hypothyroid patients. Increased levels of the protein are found in pregnancy and in acute phase conditions. In patients suspected to have a bleeding tendency, the von Willebrand test, if normal, should be repeated on two more occasions to rule out von Willebrand's disease (WHO protocol)

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