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Test ID: F_7    
Coagulation Factor VII Activity Assay, Plasma

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

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

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.

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: 65-180%

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 section in Coagulation Guidelines for Specimen Handling and Processing 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 VII activity.

 

Patients that are homozygous have levels usually less than 20% activity.

 

Patient that are heterozygous generally have levels of less than or =50% activity.

 

Newborn infants usually have levels greater than 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 one of the first to return to normal when anticoagulation is discontinued.

Clinical Reference Recommendations for 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

Special Instructions Library of PDFs including pertinent information and forms related to the test