Factor X Activity

CPT: 85260
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Test Details

Synonyms

  • Stuart Prower Factor

Use

Evaluate an isolated, prolonged PT, evaluate prolongation of both the aPTT and PT, and to document factor X deficiency6-8

Limitations

Direct Xa or thrombin inhibitor therapy may cause factitiously low results.

Methodology

Factor X activity is determined using an aPTT-based one-stage clotting time assay. Factor X-depleted plasma is used as the substrate, and the clotting time with the patient plasma is compared to the clotting time of normal pooled plasma.

Additional Information

To evaluate an isolated prolonged PT or to evaluate prolongation of both the APTT and PT and to document factor X deficiency.6-8 Factor X is a 54.8 kilodalton vitamin K-dependent glycoprotein coagulation factor that is produced by the liver.6 Normal factor X's plasma concentration is approximately 10 mg/mL and half-life is about 40 hours.6 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). The dilute Russell viper venom (dRVVT) measures the activation of factor X and will be prolonged in patients with deficiency.7,8 Congenital factor X deficiency is rare and is inherited as an autosomal recessive trait.6 This condition affects both males and females.6 A few cases of combined congenital factor II, VII, IX, and X factor deficiencies have been reported.6

Acquired deficiencies occur with significant hepatic dysfunction, with vitamin K antagonist (warfarin) therapy, and in individuals with vitamin K deficiency.6,7 Factor X deficiency may be associated with primary systemic amyloidosis.6,8 Isolated factor X deficiency may also occur in patients with respiratory infections, acute myeloid leukemia, amyloidosis, and with other malignancies.7 Acquired specific factor X inhibitors are rare in patients without congenital deficiency.6,7 Symptoms (homozygotes) include hematoma formation, postsurgical hemorrhage, menorrhagia, hematuria, and umbilical cord hemorrhage.6,7 Factor X plasma activity <30% may result in excessive bleeding following a traumatic event.6 Spontaneous bleeding similar to that observed in severe hemophilia may occur when the activity is <1%.6,7

Specimen Requirements

Specimen

Plasma, frozen

Volume

2 mL

Minimum Volume

1 mL

Container

Blue-top (sodium citrate) tube

Patient Preparation

Ideally, the patient should not be on anticoagulant therapy. Avoid warfarin (Coumadin®) therapy for two weeks prior to the test and heparin, direct Xa, and thrombin inhibitor therapies for about three days prior to testing.

Collection

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 unless the sample is collected using a winged (butterfly) collection system. With a winged blood collection set a discard tube should be drawn first to account for the dead space of the tubing and prevent under-filling of the evacuated tube.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 alternative 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. 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

Severe hemolysis; improper labeling; clotted specimen; specimen diluted with IV fluids; samples thawed in transit; improper sample type; sample out of stability

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. Adcock DM, Bethel MA, Macy PA. Coagulation Handbook. Aurora, Colo: Esoterix−Colorado Coagulation; 2006.
7. Roberts HR, Escobar MA. Less common congenital disorders of hemostasis. In: Kitchens CS, Alving BM, Kessler CM, eds. Consultative Hemostasis and Thrombosis. Philadelphia, Pa: WB Saunders Co; 2002: 57-71.
8. Triplett DA. Coagulation abnormalities. In: McClatchey KD, ed. Clinical Laboratory Medicine. 2nd ed. Philadelphia, Pa: Lippincott Williams and Wilkins; 2002:1033-1049.

References

Van Cott EM, Laposata M. Coagulation. In: Jacobs DS, DeMott WR, Oxley DK eds. Laboratory Test Handbook With Key Word Index. Hudson, Ohio: Lexi-Comp; 2001:327-358.

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
086306 Factor X Activity 3218-5 086306 Factor X Activity % 3218-5

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