Test ID: VWFX
von Willebrand Factor Activity, Plasma
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
Diagnosis of von Willebrand disease (VWD) and differentiation of VWD subtypes or differentiation of VWD from hemophilia A (Note: this activity assay is most effective when it is combined with measurement of von Willebrand factor (VWF) antigen and factor VIII coagulant activity, preferably as a panel of tests with reflexive testing and interpretive reporting [eg, VWPR/83099 von Willebrand Profile])
Monitoring therapeutic efficacy of treatment with DDAVP (desmopressin) or VWF concentrates in patients with VWD
Reflex Tests Lists test(s) that may or may not be performed, at an additional charge, depending on the result and interpretation of the initial test(s)
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| RIST | Ristocetin Cofactor, P | No | No |
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
If von Willebrand factor activity is <55%, then the von Willebrand factor ristocetin cofactor activity assay will be performed at an additional charge.
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
Latex Particle Enhanced Immunoassay
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
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: 2 mL in 2 plastic vials each containing 1 mL
Collection Instructions:
1. Specimen must be drawn prior to factor replacement therapy.
2. Spin down, remove plasma, and spin plasma again.
3. Freeze specimens immediately at < or =-40 degrees C, if possible.
4. Send specimens in the same shipping container.
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 F8A/9070 Coagulation Factor VIII Activity Assay, Plasma and VWAG/9051 von Willebrand Factor Antigen, Plasma are recommended in conjunction with von Willebrand activity.
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
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 and platelet VWF. Plasma VWF mainly reflects VWF synthesis and release from vascular endothelial cells. 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 measure platelet VWF protein. The major function of VWF (mediating platelet-platelet or platelet-vessel interaction) is most commonly assessed by measurement of plasma VWF activity.
Patients with congenital severe type 3 von Willebrand disease (VWD) have markedly decreased or immeasurably low VWF antigen in the plasma (and in the platelets), and plasma VWF activity is very low or not detectable. Patients with types 2A and 2B variants of VWD (with abnormal plasma VWF function and multimeric structure) may have normal or decreased plasma VWF antigen, but typically have decreased plasma VWF activity, and decreased higher molecular weight VWF multimers in the plasma. Patients with type 2M or type 2N VWD have normal levels of antigen, but either decreased VWF activity not caused by absence of higher molecular weight VWF multimers (type 2M VWD), or decreased factor VIII coagulant activity (type 2N VWD). Patients with type 1 VWD (with decreased but normally functioning plasma VWF) have concordantly decreased plasma VWF antigen and activity. Patients with acquired von Willebrand syndrome (AVWS) may have either normal or decreased plasma VWF antigen, and decreased VWF activity.
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%
Normal, full-term newborn infants may have mildly increased levels which reach adult levels by 90 days postnatal. Healthy, premature infants (30-36 weeks gestation) may have increased levels that reach adult levels by 180 days.
Note: Individuals of blood group "O" may have lower plasma von Willebrand factor (VWF) activity than those of other ABO blood groups, such that apparently normal individuals of blood group "O" may have plasma VWF activity 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%.
Interpretation Provides information to assist in interpretation of the test results
von Willebrand factor (VWF) activity is reduced in parallel with VWF antigen in von Willebrand disease (VWD), except in types 2A, 2B, and 2M, and some cases of acquired von Willebrand syndrome (AVWS) in which the VWF activity is disproportionately decreased relative to the level of VWF antigen.
The VWF activity may be decreased in congenital VWD or AVWS that may be associated with are variety of disorders including monoclonal gammopathies, lymphoproliferative disorders, autoimmune disorders, hypothyroidism, severe aortic stenosis, left ventricular assist device, and arteriovenous malformation.
The VWF activity may be increased in association with pregnancy or estrogen use (including oral contraceptives), acute ("acute-phase reactant") or chronic inflammation, exercise or stress, liver disease, vasculitis, and thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS). Such increases in VWF activity may obscure the laboratory diagnosis of mild VWD.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Measurement of von Willebrand factor (VWF) activity alone has limited diagnostic value. The diagnosis of von Willebrand disease (VWD) requires a combination of clinical and laboratory information. VWF activity assay results generally must be used together with assays of VWF antigen and factor VIII coagulant activity for optimum clinical utility and diagnostic efficiency.
Results may be affected by:
-Unfractionated heparin: >4.0 U/mL may cause an overestimation of the test result
-Hemoglobin: >70 mg/dL may cause the result to be underestimated
-Bilirubin: >4.2 mg/dL may cause the result to be underestimated
-Triglycerides: >1,020 mg/dL may cause the result to be underestimated
-Rheumatoid factor: >200 IU/mL may cause an overestimation of the test result
Specimens from patients who have received preparation of mouse monoclonal antibody for diagnosis or therapy may contain human antimouse antibody (HAMA). The presence of HAMA may cause an overestimation of results in immunoassays that utilize mouse monoclonal antibodies. This assay contains a blocking agent against HAMA to minimize this interference.
Supportive Data
This assay (HemosIL von Willebrand factor [VWF] activity) performed on the ACL TOP instrument demonstrates the following validation characteristics: intra- and interassay precision (CV) are < or =10%; the lower limit of detection is 3%; with excellent linearity (r [2]=0.999) up to 1,000%. For apparently healthy subjects (n=368) and for patients with type 1 von Willebrand disease (VWD) (n=57), the HemosIL VWF activity assay correlates well with the platelet agglutination assay for VWF ristocetin cofactor (RCo) activity. For patients with type 2A, 2B, or 2M VWD (independently determined by VWF:RCo, VWF antigen, and plasma VWF multimer analysis), the sensitivity and specificity of the HemosIL VWF activity is 100%. Moreover, compared to VWF:RCo, the HemosIL VWF activity is more sensitive to loss of the highest molecular weight VWF multimers among patients with AVWS. This is also reflected in type 3 VWD patients receiving Humate P therapy where the VWF activity is 10% to 20% lower than the VWF:RCo. Plasma VWF multimer analysis of these patients revealed loss of the highest molecular weight VWF multimers. Finally, a VWF activity:VWF antigen ratio >0.8 reliably excludes congenital type 2A and 2B VWD, and AVWS (including loss of the highest VWF multimers due to left ventricular assist device).
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Montgomery RR: Structure and function of von Willebrand factor. In Hemostasis and Thrombosis: Basic Principles and Clinical Practice. 4th edition. Edited by Colman RW, Hirsh J, Marder VJ, et al. Philadelphia, PA, Lippincott Williams and Wilkins, 2001, pp 249-274
2. Sadler JE, Blinder M: von Willebrand disease: diagnosis, classification, and treatment. In Hemostasis and Thrombosis: Basic Principles and Clinical Practice. 4th edition. Edited by Colman RW, Hirsh J, Marder VJ, et al. Philadelphia, PA, Lippincott Williams and Wilkins, 2001, pp 825-837
3. Tefferi A, Nichols WL: Acquired von Willebrand's disease: concise review of occurrence, diagnosis, pathogenesis and treatment. Am J Med 1997;103:536-540
4. Salem RO, Van Cott EM: A new automated screening assay for the diagnosis of von Willebrand Disease. Am J Clin Pathol 2007;127:730-735
Method Description Describes how the test is performed and provides a method-specific reference
This is a latex particle-enhanced immunoassay to quantify von Willebrand factor (VWF) activity in plasma. The activity of VWF is determined by measuring the increase of turbidity produced by the agglutination of the latex reagent. A specific anti-VWF monoclonal antibody adsorbed onto the latex reagent, directed against the platelet-binding site of VWF (glycoprotein Ib receptor), reacts with the VWF of patient plasma. The degree of agglutination is directly proportional to the activity of VWF in the sample and is determined by measuring the decrease of transmitted light caused by the aggregates. (Package insert: HemosIL von Willebrand Factor Activity, Instrumentation Laboratory, Lexington MA, 9/2006)
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.
85397
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 |
|---|---|---|
| VWFX | von Willebrand Factor Activity, P | 68324-3 |
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