Test Id : VWACT
von Willebrand Factor Activity, Plasma
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
Monitoring therapeutic efficacy of treatment with DDAVP (desmopressin) or VWF concentrates in patients with VWD
Reflex Tests
Lists tests that may or may not be performed, at an additional charge, depending on the result and interpretation of the initial tests.
| Test Id | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| RIST | Ristocetin Cofactor, P | No | No |
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
If von Willebrand factor activity is less than 55%, then the von Willebrand factor ristocetin cofactor activity assay will be performed at an additional charge.
Method Name
A short description of the method used to perform the test
Latex Immunoassay
NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test
Aliases
Lists additional common names for a test, as an aid in searching
Ristocetin cofactor
VFW Activity
TEST
Von Willebrand factor activity
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
If von Willebrand factor activity is less than 55%, then the von Willebrand factor ristocetin cofactor activity assay will be performed at an additional charge.
Specimen Type
Describes the specimen type validated for testing
Plasma Na Cit
Ordering Guidance
This activity assay is most effective when it is combined with measurement of von Willebrand factor antigen and factor VIII coagulant activity, preferably as a panel of tests with reflexive testing and interpretive reporting. See AVWPR / von Willebrand Disease Profile, Plasma.
Additional Testing Requirements
Tests for F8A / Coagulation Factor VIII Activity Assay, Plasma and VWAG / von Willebrand Factor Antigen, Plasma are recommended in conjunction with this test (von Willebrand activity).
Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
Specimen Type: Platelet-poor plasma
Collection Container/Tube: Light-blue top (3.2% sodium citrate)
Submission Container/Tube: Plastic vial (polypropylene preferred)
Specimen Volume: 2 mL in 2 vials each containing 1 mL
Collection Instructions:
1. Specimen must be collected prior to factor replacement therapy.
2. For complete instructions, see Coagulation Guidelines for Specimen Handling and Processing.
3. Centrifuge, transfer all plasma into a polypropylene vial, and centrifuge plasma again.
4. Aliquot plasma (1-2 mL per aliquot) into 2 separate polypropylene vials leaving 0.25 mL in the bottom of centrifuged vial.
5. Freeze plasma immediately (no longer than 4 hours after collection) at -20 degrees C or, ideally, < or =-40 degrees C.
6. 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.
Special Instructions
Library of PDFs including pertinent information and forms related to the test
Forms
If not ordering electronically, complete, print, and send a Coagulation Test Request (T753) with the specimen.
Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.
0.5 mL
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
| Gross icterus | Reject |
Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Plasma Na Cit | Frozen | 14 days |
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
Monitoring therapeutic efficacy of treatment with DDAVP (desmopressin) or VWF concentrates in patients with VWD
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
If von Willebrand factor activity is less than 55%, then the von Willebrand factor ristocetin cofactor activity assay will be performed at an additional charge.
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 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.
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 nondetectable. 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 may have either normal or decreased plasma VWF antigen and decreased VWF activity.
Note: VWF activity measurement 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, AVWPR / von Willebrand Disease Profile, Plasma).
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 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 >1020 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.
Clinical Reference
Recommendations for in-depth reading of a clinical nature
1. Montgomery RR. Structure and function of von Willebrand factor. In: Colman RW, Hirsh J, Marder VJ, et al, eds. Hemostasis and Thrombosis: Basic Principles and Clinical Practice. 4th ed. Lippincott Williams and Wilkins; 2001:249-274
2. Sadler JE, Lillicrap DL. von Willebrand disease: diagnosis, classification, and treatment. In: Marder VJ, Aird WC, Bennett JS, Schulman S, White II GC, eds. Hemostasis and Thrombosis: Basic Principles and Clinical Practice. 6th ed. Lippincott Williams and Wilkins; 2013:670-683
3. Favaloro EJ and Lippi G. eds. Hemostasis and Thrombosis, Methods and Protocols. 1st ed. Humana Press; 2017
4. Salem RO, Van Cott EM. A new automated screening assay for the diagnosis of von Willebrand Disease. Am J Clin Pathol. 2007;127(5):730-735
5. Favaloro EJ, Lippi G, eds. Hemostasis and Thrombosis: Methods and Protocols. Humana Press; 2017.
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; 09/2006)
PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information
Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.
Monday through Friday
Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.
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
Indicates the location of the laboratory that performs the test
Fees :
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.
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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 instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.
This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.
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 Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
CPT codes are provided by the performing laboratory.
CPT codes are provided by the performing laboratory.
85397
LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.
| Test Id | Test Order Name | Order LOINC Value |
|---|---|---|
| VWACT | von Willebrand Factor Activity, P | 68324-3 |
| Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
|---|---|---|
| VWACT | von Willebrand Factor Activity, P | 68324-3 |