Find Locations
For hours, walk-ins and appointments.Synonyms
- Stuart Factor
- Stuart Prower Factor
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.
Expected Turnaround Time
2 - 3 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Related Information
Related Documents
For more information, please view the literature below.
Procedures for Hemostasis and Thrombosis: A Clinical Test Compendium
Specimen Requirements
Specimen
Plasma, frozen
Volume
1 mL
Container
Blue-top (sodium citrate) tube
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 No. 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
Test Details
Use
The chromogenic factor X activity test can be useful in monitoring patients on vitamin K antagonist therapy where baseline PT is prolonged.
Limitations
Direct Xa inhibitor therapy may cause factitiously low results.
This test was developed, and its performance characteristics determined, by Labcorp. It has not been cleared or approved by the Food and Drug Administration.
Methodology
Factor X is activated by Russell viper venom which, in turn, hydrolyzes a chromogenic substrate to produce color.
Reference Interval
• Nonanticoagulated subjects: 82% to 151%
• Anticoagulant therapeutic range: 17% to 43% corresponds to an INR range of 2.0−3.56
Additional Information
Factor X is a 54.8 kilodalton vitamin K-dependent glycoprotein coagulation factor that is produced by the liver.7 Normal factor X's plasma concentration is approximately 10 mg/mL with a half-life of about 40 hours.7 Factor X activation occurs by both the extrinsic and intrinsic pathways. Factor X deficiency should be considered when a patient with bleeding history has both extended protime (PT) and activated partial thromboplastin time (aPTT).
Oral anticoagulation with warfarin inhibits vitamin K-dependent carboxylation of several procoagulant factors, including factor X. Overdosing with warfarin can increase the risk of hemorrhage and inadequate dosing decreases the efficacy of anticoagulation. Unfortunately, a large number of factors can affect the pharmacological potency of these oral anticoagulants. These factors are reviewed in considerable detail in the American Heart Association/American College of Cardiology Foundation Guide to Warfarin Therapy.8 The prothrombin time (PT) test is sensitive to deficiencies of vitamin K-dependent factors and is commonly used to monitor warfarin therapy. In some cases, however, patients with lupus anticoagulants can have extended PT. Several studies have suggested that this can complicate the management of anticoagulant therapy with the prothrombin time.6,9,10 The chromogenic factor X activity test can be useful in monitoring patients where baseline PT is prolonged.
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. Moll S, Ortel TL. Monitoring warfarin therapy in patients with lupus anticoagulants. Ann Intern Med. 1997 Aug 1; 127(3):177-185. 9245222
7. Adcock DM, Bethel MA, Macy PA. Coagulation Handbook. Aurora, Colo: Esoterix−Colorado Coagulation; 2006.
8. Hirsh J, Fuster V, Ansell J, Halperin JL, American Heart Association, American College of Cardiology Foundation. American Heart Association/American College of Cardiology Foundation guide to warfarin therapy. Circulation. 2003 Apr 1; 107(12):1692-1711. 12668507
9. Sanfelippo MJ, Sennet J, McMahon EJ. Falsely elevated INRs in warfarin-treated patients with lupus anticoagulant. WMJ. 2000 Jun; 99(3):62-64, 43. 10927985
10. Robert A, Le Querrec A, Delahousse B, et al. Control of oral anticoagulation in patients with the antiphospholipid syndrome−influence of the lupus anticoagulant on International Normalized Ratio. Groupe Méthodologie en Hémostase du Groupe d'Études sur l'Hémostases et la Thrombose. Thromb Haemost. 1998 Jul; 80(1):99-103. 9684793
References
Adcock DM, Gosselin R. Direct oral anticoagulants (DOACs) in the laboratory: 2015 review. Thromb Res. 2015 Jul; 136(1):7-12. 25981138
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 117904 | Factor X, Chromogenic | 28657-5 | 117908 | Factor X, Chromogenic | % | 28657-5 |
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