F_2 - Clinical: Coagulation Factor II Activity Assay, Plasma

Test Catalog

Test Name

Test ID: F_2    
Coagulation Factor II Activity Assay, Plasma

Useful For Suggests clinical disorders or settings where the test may be helpful

Diagnosing a congenital deficiency (rare) of coagulation factor II


Evaluating acquired deficiencies associated with liver disease or vitamin K deficiency, oral anticoagulant therapy, and antibody-induced deficiencies (eg, in association with lupus-like anticoagulant)


Determining warfarin treatment stabilization in patients with nonspecific inhibitors (ie, lupus anticoagulant)


Determining degree of anticoagulation with warfarin to correlate with level of protein S


Investigation of prolonged prothrombin time or activated partial thromboplastin time

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Factor II (prothrombin) is a vitamin K-dependent serine protease synthesized in liver. It participates in the final common pathway of coagulation, as the substrate for the prothrombinase enzyme complex. Prothrombin is the precursor of thrombin (IIa) which converts fibrinogen to fibrin. Plasma biological half-life is about 3 days.


Deficiency of factor II may cause prolonged prothrombin time and activated partial thromboplastin time. Deficiency may result in a bleeding diathesis.

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.

Adults: 75-145%

Normal, full-term newborn infants or healthy premature infants may have decreased levels (> or =25%) which may remain below adult levels for > or =180 days postnatal.*

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

Interpretation Provides information to assist in interpretation of the test results

Liver disease, vitamin K deficiency, or warfarin anticoagulation can cause decreased factor II activity.


Homozygotes generally have levels of <25%


Heterozygotes generally have levels of <50%


Normal newborn infants may have levels of 25% to 50%

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Factor II is 1 of the last vitamin K-dependent coagulation factors to decrease after starting warfarin therapy and 1 of the last to return to normal when anticoagulation is discontinued. It may take 10 to 14 days for a return to baseline levels.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Lancellotti S, De Cristofaro R: Congenital prothrombin deficiency. Semin Thromb Hemost 2009 Jun;35(4):367-381

2. Peyvandi F, Bolton-Maggs PH, Batorova A, De Moerloose P: Rare bleeding disorders. Haemophilia 2012 Jul;18 Suppl 4:148-153

3. Girolami A, Scandellari R, Scapin M, Vettore S: Congenital bleeding disorders of the vitamin K-dependent clotting factors. Vitam Horm 2008;78:281-374

4. Brenner B, Kuperman AA, Watzka M, Oldenburg J: Vitamin K-dependent coagulation factors deficiency. Semin Thromb Hemost 2009 Jun;35(4):439-446

Special Instructions and Forms Library of PDFs including pertinent information and consent forms, specimen collection and preparation information, test algorithms, and other information pertinent to test