von Willebrand Factor (vWF) Profile

CPT: 85240; 85245; 85246
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Test Details

Test Includes

Factor VIII; von Willebrand factor activity; von Willebrand factor antigen

Use

Diagnose von Willebrand factor (vWF) deficiency6,8-10

Limitations

A number of transient clinical conditions can raise the vWF levels of individuals with congenital deficiency into the normal range.8 vWF is an acute phase reactant and levels can increase due to stress, inflammation, acute infection, physical exercise, and following surgery.8 Levels can also increase with estrogen administration for contraception or hormone replacement.8 vWF levels are increased two- to threefold in the second and third trimesters of pregnancy.10 Individuals with type O blood tend to have approximately 30% lower vWF levels than those with other blood types.10

Methodology

See individual tests.

Reference Interval

• von Willebrand factor (vWF) activity: 50% to 150%

• von Willebrand factor (vWF) antigen: 50% to 150%

• Factor VIII activity: 50% to 150%

Average vWF levels (both antigen and activity) tend to vary by blood type.6 One study found the mean vWF levels by blood type to be as follows:7

• Type O: 74.8%

• Type A: 105.6%

• Type B: 116.9%

• Type AB: 123.3%

Additional Information

vWF is produced by megakaryocytes and endothelial cells.8 The vWF protein polymerizes in plasma into multimers of up to 100 subunits that range in size from 0.5 to 20 million daltons.6,8 vWF's plasma half-life is about 24 hours.

vWF performs two major functions in hemostasis.8,9 vWF acts as a cross-linking protein that connects platelets to each other and to subendothelial cells at the site of vascular damage. This functionality is dependent on the presence of high molecular weight multimers of vWF. vWF also serves as an obligate carrier of factor VIII in plasma. Functional vWF serves to protect factor VIII from proteolytic degradation and effectively increases its half-life fivefold.10 Effective factor VIII binding is not dependent on the presence of large multimeric vWF complexes.9 The assessment of vWF activity requires two tests to evaluate these two functions. The vWF activity (ristocetin cofactor) assay reflects the effectiveness of the patient vWF in supporting platelet adhesion. Factor VIII levels can be diminished due to low vWF levels or due to ineffective factor VIII binding by a defective vWF.

von Willebrand disease (vWD) should be considered in the differential diagnosis of any case where a patient with bleeding history has a normal protime (PT) and activated partial thromboplastin time (aPTT). The aPTT can be extended in severe vWD due to diminished levels of factor VIII that result from inadequate vWF binding.6

vWD is the most common congenital bleeding disorder known with an estimated incidence of 1 in 100 individuals;8,9 however, the clinical incidence of vWD is much lower because many of these individuals remain asymptomatic and are never diagnosed.9,10 The severity of bleeding for patients with vWD can vary, even among family members with the same defect.8,10 Bleeding symptoms are usually similar to those seen with platelet disorders and other defects in primary hemostasis.9 A typical symptom of an individual with a defect in primary hemostasis would be profuse bleeding from small cuts with the need for prolonged application of pressure to stop the bleeding.11 Many individuals with less severe forms of vWD are first identified because of a history of recurrent nosebleeds (epistaxis).8 vWD patients generally present with mucocutaneous bleeding characterized by epistaxis, ecchymosis, easy bruising, gingival bleeding, menorrhagia, or genitourinary bleeding.8,11 Three different types of vWD can be distinguished based on the results of laboratory tests and the severity of symptoms.8

Type 1: A genetic defect causing diminished production of functional vWF. Laboratory tests typically reveal correspondingly low levels of both vWF antigen and activity.8 This is the most common form, representing approximately 75% of cases.10 Type 1 vWD is usually inherited as an autosomal dominant mutation.8 The risk of bleeding in women with vWD is increased in the postpartum period when vWF levels drop precipitously from the elevated levels developed during pregnancy.9

Note: While individuals with very low vWF levels (ie, <30%) are more likely to have an identifiable genetic basis for the condition, individuals with moderately diminished levels (30% to 50%) may be classified simply as having low vWF, not Type I vWF disease.12 It is often difficult to directly attribute increased bleeding to low vWF in these patients because bleeding associated with moderately diminished vWF is generally mild and complaints of mild bleeding tendency are commons.12

Type 2: A number of forms of type 2 vWD are characterized by the presence of dysfunctional vWF protein. Individuals with these forms represent approximately 25% of cases of vWD.10 Individuals with type 2 vWD often have normal or slightly low levels of vWF antigen with relatively lower levels vWF activity.8 Type 2 vWD can be inherited as either dominant or recessive mutations.8 Individuals with heterozygous type 2 vWD generally suffer from more severe bleeding than those with type 1 vWD.

Type 3: This relatively rare form of vWD occurs as the result of homozygous or compound heterozygous defects producing undetectable levels of vWF antigen and activity. Patients with this form of vWD generally have the worst bleeding symptoms. These individuals can present with spontaneous bleeding, significant postsurgical bleeding, or gastrointestinal hemorrhage.8 Factor VIII levels can be low or absent in type 3 patients resulting in bleeding similar to that seen in hemophilia A.9 It is important to distinguish between these two conditions because the methods of treatment are very different.

Acquired vWD is very rare with less than 100 cases documented in the literature.13 The majority of cases have been reported in association with autoimmune or clonal proliferative conditions.13 Acquired vWD has been reported in patients with systemic lupus erythematosus, antiphospholipid syndrome, and hypothyroidism. Other conditions associated with acquired vWD are Wilms' tumor and congenital cardiovascular disease.8,13 Autoantibodies to vWF can sometimes cause vWD in elderly individuals with multiple myeloma, lymphoproliferative disorders, or collagen vascular disease.8

Specimen Requirements

Specimen

Plasma (platelet poor), frozen

Volume

3 mL

Minimum Volume

2 mL

Container

Blue-top (sodium citrate) tube

Patient Preparation

As VWF and FVIII are acute-phase reactant proteins, patients should be at ease when blood is drawn. Undue stress, such as a crying child or very recent exercise may elevate VWF levels, and these conditions should be avoided. Certain anticoagulant therapies, such as heparin, direct thrombin inhibitors, and direct Xa inhibitors may interfere with FVIII activity results but will not interfere with analysis of VWF. Do not draw from an arm with a heparin lock or heparinized catheter.

Collection

Citrated plasma samples should be collected by double centrifugation. Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.1 Evacuated collection tubes must be filled to completion to ensure a proper blood to anticoagulant ratio.2,3 The sample should be mixed immediately by gentle inversion at least six times to ensure adequate mixing of the anticoagulant with the blood. A discard tube is not required prior to collection of coagulation samples, except when using a winged blood collection device (ie, "butterfly"), in which case a discard tube should be used.4,5 When noncitrate tubes are collected for other tests, collect sterile and nonadditive (red-top) tubes prior to citrate (blue-top) tubes. Any tube containing an alternate anticoagulant should be collected after the blue-top tube. Gel-barrier tubes and serum tubes with clot initiators should also be collected after the citrate tubes. Centrifuge for 10 minutes and carefully remove 2/3 of the plasma using a plastic transfer pipette, being careful not to disturb the cells. Deliver to a plastic transport tube, cap, and recentrifuge for 10 minutes. Use a second plastic pipette to remove the plasma, staying clear of the platelets at the bottom of the tube. Transfer the plasma into a LabCorp PP transpak frozen purple tube with screw cap (LabCorp N° 49482). Freeze immediately and maintain frozen until tested. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Please print and use the Volume Guide for Coagulation Testing to ensure proper draw volume.

Storage Instructions

Freeze

Causes for Rejection

Gross hemolysis; clotted specimen; frozen specimen thawed in transit; improper labeling; improper collection tube

Clinical Information

Special Instructions

If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted. Refer to Coagulation Collection Procedures for directions.

Footnotes

1. Adcock DM, Kressin DC, Marlar RA. Effect of 3.2% vs 3.8% sodium citrate concentration on routine coagulation testing. Am J Clin Pathol. 1997 Jan; 107(1):105-110. 8980376
2. Reneke J, Etzell J, Leslie S, Ng VL, Gottfried EL. Prolonged prothrombin time and activated partial thromboplastin time due to underfilled specimen tubes with 109 mmol/L (3.2%) citrate anticoagulant. Am J Clin Pathol. 1998 Jun; 109(6):754-757. 9620035
3. National Committee for Clinical Laboratory Standardization. Collection, Transport, and Processing of Blood Specimens for Coagulation Testing and General Performance of Coagulation Assays; Approved Guideline. 5th ed. Villanova, Pa: NCCLS; 2008. Document H21-A5:28(5).
4. Gottfried EL, Adachi MM. Prothrombin time and activated partial thromboplastin time can be performed on the first tube. Am J Clin Pathol. 1997 Jun; 107(6):681-683. 9169665
5. McGlasson DL, More L, Best HA, Norris WL, Doe RH, Ray H. Drawing specimens for coagulation testing: Is a second tube necessary? Clin Lab Sci. 1999 May-Jun; 12(3):137-139. 10539100
6. Van Cott EM, Laposata M. Coagulation. In: Jacobs DS, DeMott WR, Oxley DK eds.Laboratory Test Handbook With Key Word Index. Hudson, OH: Lexi-Comp; 2001:327-358.
7. Gill JC, Endres-Brooks J, Bauer PJ, Marks WJ Jr, Montgomery RR. The effect of ABO blood group on the diagnosis of von Willebrand disease. Blood. 1987 Jun; 69(6):1691-1695. 3495304
8. Adcock DM, Bethel MA, Macy PA. Coagulation Handbook. Aurora, Colo: Esoterix−Colorado Coagulation; 2006.
9. Brandt JT. Laboratory evaluation of platelet disorders. In: McClatchey KD, ed. Clinical Laboratory Medicine. 2nd ed. Philadelphia, Pa: Lippincott Williams and Wilkins; 2002:1010-1032.
10. Rick ME. von Willebrand disease. In: Kitchens CS, Alving BM, Kessler CM eds. Consultative Hemostasis and Thrombosis Philadelphia, Pa: WB Saunders Co; 2002:91-102.
11. Liu MC, Kessler CM. A systemic approach to the bleeding patient. In: Kitchens CS, Alving BM, Kessler CM, eds. Consultative Hemostasis and Thrombosis. Philadelphia, Pa: WB Saunders Co;2002:181-196.
12. Nichols WL, Hultin MB, James AH, et al. von Willebrand disease (VWD): Evidence-based diagnosis and management guideline, The National Heart, Lung, and Blood Institute (NHLB) Expert Panel report (USA). Haemophilia. 2008 Mar; 14(2):171-232. 18315614
13. Tefferi A, Nichols WL. Acquired von Willebrand disease: Concise review of occurrence diagnosis, pathogenesis, and treatment. Am J Med. 1997 Dec; 103(6):536-540. 9428838

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
084715 von Willebrand Profile 086264 Factor VIII Activity % 3209-4
084715 von Willebrand Profile 086280 von Willebrand Factor (vWF) Ag % 27816-8
084715 von Willebrand Profile 164509 vWF Activity % 6014-5
Reflex Table for vWF Activity
Order Code Order Name Result Code Result Name UofM Result LOINC
Reflex 1 910377 Coag Studies Interp Report 910378 Interpretation 21026-0
Reflex Table for vWF Activity
Order Code Order Name Result Code Result Name UofM Result LOINC
Reflex 1 910377 Coag Studies Interp Report 910379 PDF Image Not Available
Reflex Table for vWF Activity
Order Code Order Name Result Code Result Name UofM Result LOINC
Reflex 1 910377 Coag Studies Interp Report 910382 Litholink N/A

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