Factor 2 Activity

Abbrev Code:F2   
Order Code:LAB303Order Name:Factor 2 Assay
Synonyms:Prothrombin Assay; Factor II Activity
Methodology:Thromboplastin clotting time correction of Factor 2 deficient plasma. Patient dilutions are compared to a known set of standard dilutions and a percentage is determined.
CPT Codes: 85210 x1, 85210 x1
Turnaround Time:Within 8 hours if received into the testing laboratory by 12 p.m. Testing performed 6 days per week. With pre-notification, STATs are done within 1 hour after receipt in the testing laboratory.
Special Instructions:This test is different from the Prothrombin 20210 Mutation PCR test.
Associated Links:

Specimen Collection and Processing for Coagulation Specimens

Collection Instructions

Optimal Volume:2.7 mL (in 3 mL tube) - filled to fill line on the tube.
Minimum\Peds Volume:1.8 mL (in 2 mL tube) - filled to fill line on the tube.
Container:Blue Na Citrate, 3.2% - fill to fill line on tube
Collection Instructions:See link to Specimen Collection and Processing for Coagulation Specimens.
Causes for Rejection:Underfilled tubes, overfilled tubes, clotted specimens, not received or processed and frozen within 4 hours of collection or, specimen thawed during transit.

Processing and Shipping

Specimen Processing:
  • Process for Platelet Poor Plasma within 4 hours of collection.
  • Aliquot plasma, place clear tape around label, and freeze at -20C or on dry ice within 4 hours of collection.
  • If multiple tests are collected on 1 blue top, split each blue top into 2 aliquots. Minimum 0.5 mL per tube.
  • A maximum of 6 aliquots are needed per collection.
See link to Specimen Collection and Processing for Coagulation Specimens.
Shipping Instructions:
  • Ensure specimen is frozen before shipping.
  • Ship on dry ice, sample must remain frozen during shipping.
See link to Specimen Collection and Processing for Coagulation Specimens.
Test Performed at or Referral Lab UM Special Coag (K)  (UMMC East Bank)


Critical Range:Less than 10%
Reference Range:

Less than 1 d


1-4 d


5-29 d


30-89 d


90-179 d


180-364 d


1 y and older




Therapeutic Range:With Coumadin therapy: 15-25%
Use:Factor 2 is a common pathway factor. A deficiency can result in a moderately severe bleeding disorder. Also used to monitor Coumadin therapy in patients with lupus inhibitors. Factor 2 is dependent on Vitamin K for its carboxylation. It is decreased in Vitamin K deficiency/Coumadin therapy. Prothrombin is the clinically critical factor that needs to be reduced to have effective anticoagulation with Coumadin. Therapeutic level for Coumadin therapy is 15-25%.

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