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Test Code MISCLM Coagulation Factor X Chromogenic Activity Assay, Plasma

Additional Codes



Reporting Name

Factor X Chromogenic Activity Assay

Useful For

Monitoring warfarin anticoagulant therapy, especially in patients whose plasma contains lupus anticoagulants that interfere with baseline prothrombin time/international normalized ratio and in patients receiving the drug Argatroban who are being transitioned to warfarin

Method Name

Chromogenic Assay

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type

Plasma Na Cit

Specimen Required

See Coagulation Studies in Special Instructions.


Specimen Type: Platelet-poor plasma

Collection Container/Tube: Light-blue top (citrate)

Submission Container/Tube: Polypropylene vial

Specimen Volume: 1 mL

Collection Instructions:

1. Spin down, remove plasma, and spin plasma again.

2. Freeze specimen immediately at ≤-40° 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. If priority specimen, mark request form, give reason, and request a call-back.

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Plasma Na Cit Frozen 14 days

Reject Due To


Mild OK; Gross reject


Mild OK; Gross reject


Mild OK; Gross reject



Special Instructions

Reference Values

≥18 years of age: 60%-140%

Chromogenic Factor X activity generally correlates with the one-stage factor X activity. In full term or premature neonates, infants, and children, the one-stage factor X activity* is lower than adult reference range and progressively rises to the adult reference range by adolescence. However, no similar data for the chromogenic factor X activity have been published.

*See Pediatric Hemostasis References in Coagulation Studies in Special Instructions.

Day(s) and Time(s) Performed

Monday through Friday

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
FXCH Factor X Chromogenic Activity Assay In Process


Result ID Test Result Name Result LOINC Value
FXCH Factor X Chromogenic Activity Assay 33984-6

Test Classification

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 U.S. Food and Drug Administration.

Analytic Time

1 day


If not ordering electronically, complete, print, and send a Coagulation Test Request Form (T753) with the specimen (