Coagulation Factor VII Activity Assay, Plasma
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Factor VII is a vitamin K-dependent serine protease synthesized in the liver. It is a component of the extrinsic coagulation scheme, measured by the prothrombin time. Plasma biological half-life is about 3 to 6 hours. Deficiency may result in a bleeding diathesis.
Diagnosing congenital deficiency of coagulation factor VII
Evaluating acquired deficiencies associated with liver disease, oral anticoagulant therapy, and vitamin K deficiency
Determining degree of anticoagulation with warfarin to correlate with level of protein C
Investigation of a prolonged prothrombin time
Liver disease, vitamin K deficiency, or warfarin anticoagulation can cause decreased factor VII activity.
Heterozygotes generally have levels of < or =50%.
Homozygotes have levels usually <20%.
Newborn infants usually have levels > or =25%.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Factor VII is the first vitamin K-dependent coagulation factor to decrease after starting warfarin therapy and 1 of the first to return to normal when anticoagulation is discontinued.
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.
Normal, full-term newborn infants or healthy premature infants may have decreased levels (> or =20%) which increase within the first postnatal week but may not reach adult levels for > or =180 days postnatal.*
*See Pediatric Hemostasis References in Coagulation Studies in Special Instructions.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Girolami A, Scandellari R, Scapin M, Vettore S: Congenital bleeding disorders of the vitamin K-dependent clotting factors. Vitam Horm 2008;78:281-374
2. Brenner B, Kuperman AA, Watzka M, Oldenburg J: Vitamin K-dependent coagulation factors deficiency. Semin Thromb Hemost 2009 Jun;35(4):439-446
3. Mariani G, Bernardi F: Factor VII deficiency. Semin Thromb Hemost 2009 Jun;35(4):400-406