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von Willebrand Factor Cleaving Protease
|Approval req'd?||Yes, for any stat requests contact either dr. Scott Kogan or Dr. Andrew Leavitt for approval.|
|Test group||von Willebrand|
|Collection Instructions||1. Check the expiration date on the label of the blue top vacutainer before drawing the patient.
2. For blood collection in a sodium citrate blue top, the tube must be filled to above the Minimum Fill Indicator on the tube. It is crucial to wait and allow the tube to stop filling before removing it from the needle.
3. With use of a butterfly needle, draw about 1 cc using a separate blue top to remove air from tubing, discard the first tube and then draw a second blue top tube filled to the full extent of the vacuum.
4. Tubes should not be filled past the Maximum Fill dashed line by either using a syringe or removing the tube cap.
|Container type||Blue top filled to full extent of vacuum|
|Amount to Collect||2.7 mL blood|
|Sample type||Citrated platelet poor plasma|
|Preferred volume||1 mL plasma|
|Min. Volume||0.5 mL plasma|
|UCSF Rejection Criteria||Samples collected in outdated blue top vacutainer. Over-filled or under-filled tubes may be rejected Marked hemolysis or hyperbilirubinemia|
|Processing notes||Freeze plasma at -20C. Order Quest test 14532 "VWF Protease Activity with Reflex to Protease Inhibitor".
If the Reflex test for Protease Inhibitor is required, the test code "S13IB" will be ordered to bill the additional charge when the results are entered at China Basin.
For B&T patients order LabCorp test code #844200. LabCorp will forward the sample to BCSW
|Ref Lab Rejection Criteria||Marked hemolysis or hyperbilirubinemia|
|Critical value||Quest Priority-2: Absent activity|
|Turn around times||Set up 2x per week. Turnaround 10-14 days|
|Reflex?||Yes, If the test for Protease Inhibitor is required, it will be ordered and billed at an additional charge.|
|Additional information||Demonstration of von Willebrand Factor Cleaving Protease deficiency may be important in the diagnosis and the provision of effective therapy in Thrombotic thrombocytopenic purpura (TTP).
Absent or low levels of ADAMTS13 activity may allow the accumulation of ultra-large von Willebrand factor multimers (ULVWF) in plasma. It is hypothesized that these ULVWF cause the intravascular platelet aggregation characteristic of TTP.
Note: a normal ADAMTS13 activity does not exclude the diagnosis of TTP.
Activity levels below 10% are seen in acute and relapsing idiopathic (autoimmune) thrombotic thrombocytopenic purpura (TTP) but also in a rare hereditary gene mutation of VWF protein at the cleavage site. Activity levels between 10 and 30% may be seen in instances where immunosuppressive therapy or recent plasmapheresis exchange has been started. Mild decreases in ADAMTS-13 acitivty (35-70%) are seen in a wide variety of conditions including metastatic cancer, neonates, serious infections and cirrhosis of the liver.
The ADAMTS-13 activity is an ELISA assay using GST-vWF73 substrate. This assay is not affected by hyperbilirubinemia (up to 20 mg/dL) or hemolysis (up to 500 mg/dL). This test is performed using a kit that has not been approved or cleared by the FDA. The analytical performance characteristics of this test have been determined by Quest Diagnostics Nichols Institute, San Juan Capistrano. This test should not be used for diagnosis without confirmation by other medically established means.
Inhibitors are automatically performed when activity levels are ≤40%.
|CPT coding||85247-90 (activity), 85335-90 (inhibitor)|
|Last Updated||9/23/2013 4:19 PM|