Test ID: VWAG
von Willebrand Factor Antigen, Plasma
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
von Willebrand factor antigen measurement is most effective when it is combined with measurement of von Willebrand factor ristocetin cofactor activity and factor VIII coagulant activity, preferably as a panel of tests with reflexive testing and interpretive reporting. Within this context, von Willebrand factor antigen measurement can be useful for:
-Diagnosis of von Willebrand disease and differentiation of von Willebrand disease subtype
-Differentiation of von Willebrand disease from hemophilia A (in conjunction with factor VIII coagulant assay)
Monitoring therapeutic efficacy of treatment with DDAVP (desmopressin) or von Willebrand factor concentrates in patients with von Willebrand disease
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Method Name A short description of the method used to perform the test
Automated Latex Immunoassay (LIA)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
VON WILLEBRAND ANTIGEN
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
See Coagulation Studies in Special Instructions.
Specimen Type: Platelet-poor plasma
Collection Container/Tube: Light-blue top (citrate)
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions:
1. Spin down, remove plasma, and spin plasma again.
2. Freeze specimen immediately at < or =-40 degrees C, if possible.
Additional Information:
1. Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.
2. Each coagulation assay requested should have its own vial.
3. Tests for VWFX/89792 von Willebrand Factor Activity, Plasma and F8A/9070 Coagulation Factor VIII Activity Assay, Plasma are recommended in conjunction with von Willebrand antigen.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | Mild OK; Gross reject |
| Lipemia | Mild OK; Gross reject |
| Icterus | NA |
| Other | NA |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Plasma Na Cit | Frozen | 14 days |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
The von Willebrand factor (VWF) is a multimeric adhesive glycoprotein that is important for platelet-platelet and platelet-vessel hemostatic interactions. In addition, plasma VWF serves as a carrier protein for coagulation factor VIII, stabilizing its procoagulant activity. VWF circulates in the blood in 2 distinct compartments; plasma VWF mainly reflects VWF synthesis and release from vascular endothelial cells, and platelet VWF (about 10% of the blood VWF) reflects VWF synthesis by bone marrow megakaryocytes with storage primarily in the alpha granules of circulating platelets. VWF antigen measurement assesses the mass of plasma VWF protein, but does not reflect VWF functions or platelet VWF. The major function of VWF (mediating platelet-platelet or platelet-vessel interaction) is most commonly assessed by measurement of plasma ristocetin cofactor activity.
Decreased VWF antigen may be seen in:
-Congenital von Willebrand disease
-Acquired VWD that may be associated with monoclonal gammopathies, lymphoproliferative disorders, autoimmune disorders, and hypothyroidism
Increased VWF antigen may be seen in association with:
-Pregnancy and/or estrogen use
-Inflammation (acute-phase reactant)
-Exercise or stress
-Liver disease
-Vasculitis
-Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
55-200%
Note: Individuals of blood group "O" may have lower plasma von Willebrand factor (VWF) antigen than those of other ABO blood groups, such that apparently normal individuals of blood group "O" may have plasma VWF antigen as low as 40% to 50%, whereas the lower limit of the reference range for individuals of other blood groups may be 60% to 70%.
Children: Neonates, infants, and children have normal or mildly increased plasma VWF antigen, with respect to the adult reference range.
Interpretation Provides information to assist in interpretation of the test results
von Willebrand factor (VWF) antigen assay results generally must be used together with assays of VWF ristocetin cofactor activity and factor VIII coagulant activity, for optimum clinical utility and diagnostic efficiency. The diagnosis of von Willebrand disease (VWD) requires a combination of clinical and laboratory information. We suggest ordering VWPR/83099 von Willebrand Profile.
Patients with congenital severe type III VWD have a markedly decreased or undetectable level of VWF antigen in the plasma (and in the platelets), in addition to a plasma ristocetin cofactor activity that is very low or not detectable.
Patients with types IIA and IIB variants of VWF (with abnormal plasma VWF function and multimeric structure) may have normal or decreased plasma VWF antigen. However, they typically have decreased plasma ristocetin cofactor activity, along with decreased higher molecular-weight VWF multimers in the plasma.
Patients with types IIM or IIN VWD have normal levels of VWF antigen. In spite of this, they either have decreased vWF ristocetin cofactor activity, not caused by absence of higher molecular weight vWF multimers (type IIM VWD), or decreased factor VIII coagulant activity (type IIN VWD)
Patients with type I VWD (with decreased but normally functioning plasma VWF) have concordantly decreased plasma VWF antigen and ristocetin cofactor activity.
Patients with acquired VWD may have either normal or decreased plasma VWF antigen.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Lipemic specimens may lead to an underestimation of the von Willebrand factor (VWF) level.
The presence of rheumatoid factor may lead to an overestimation of the VWF level.
VWF is an acute-phase reactant and may be elevated above baseline in association with a variety of conditions including inflammation, stress, exercise, liver disease, pregnancy or estrogen therapy. Baseline VWF levels also increase with aging. These conditions may obscure diagnosis of the milder forms of von Willebrand disease (VWD). Repeat testing may be indicated.
Low normal levels of VWF antigen do not exclude possible diagnosis of VWD.
Borderline low or slightly decreased levels of VWF antigen may be observed in clinically normal individuals of blood group "O."
Supportive Data
Mayo studies demonstrate excellent concordance between the enzyme-linked immunosorbent assay and this automated latex immunoassay (LIA) (r[2]=0.95) in about 80 patient specimens (with von Willebrand factor [VWF] antigen ranging from 3% to 800%), and satisfactory concordance between VWF antigen by LIA and ristocetin cofactor activity (r[2]=0.88).
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Sadler JE, Blinder M: von Willebrand disease: diagnosis, classification and treatment. In Hemostasis and Thrombosis: Basic Principles and Clinical Practice. 5th edition. Edited by RW Colman, VJ Marder, AW Clowes, et al. Baltimore, MD, Lippincott Williams & Wilkins, 2006, pp 905-921
2. Eby C, Chance D, Oliver D: A multicenter evaluation of ATA-LIATEST VWF: A new latex particle immunoassay for von Willebrand factor antigen. Clin Hemostasis Rev 1997;11:16-17
3. Rodeghiero F, Castaman G, Tosetto A: Von Willebrand factor antigen is less sensitive then ristocetin cofactor for the diagnosis of type K von Willebrand disease – Results based on an epidemiological investigation. Thromb Haemost 1990;64:349-352
4. Triplett DA: Laboratory diagnosis of von Willebrand’s disease. Mayo Clin Proc 1991;66:832-840
Method Description Describes how the test is performed and provides a method-specific reference
This assay is performed using the HemosIL von Willebrand Factor Antigen Kit on the Beckman Coulter ACL TOP. This is a latex immunoassay method using microlatex particles coated with specific rabbit polyclonal antibody directed against von Willebrand factor (VWF). In the presence of VWF antigen, antibody-coated latex particles agglutinate to form aggregates of diameters greater than the wavelength of the light passing through the sample and more light is absorbed as aggregation increases. The increase in absorption is proportional to the concentration of VWF antigen present in the sample. (Veyradier A, Fressinaud E, Sigaud M, et al: A new automated method for von Willebrand factor antigen measurement using latex particles. Thromb Haemost 1999;81:320-321)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Saturday
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
85246
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| VWAG | von Willebrand Factor Ag, P | 27816-8 |
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