Test Catalog

Test ID: FACTV    
Coagulation Factor V Activity Assay, Plasma

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

Diagnosing congenital deficiencies (rare) of coagulation factor V


Evaluating acquired deficiencies associated with liver disease, factor V inhibitors, myeloproliferative disorders, and intravascular coagulation and fibrinolysis


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 V is a vitamin K-independent protein synthesized in the liver and in other tissues (endothelium, megakaryocytes/platelets). In its thrombin-activated form (factor Va), it serves as an essential cofactor in the prothrombinase enzyme complex, which converts prothrombin to thrombin (the prothrombinase complex consists of the enzyme, activated factor X, factor Va cofactor, a phospholipid surface, and calcium).


Deficiency of factor V may cause prolonged prothrombin time and activated partial thromboplastin time and may result in a bleeding diathesis. Plasma biological half-life varies from 12 to 36 hours.


Platelets contain 20% to 25% of the factor V in blood. Factor V (also known as labile factor) is highly susceptible to proteolytic inactivation, with the potential for spuriously decreased assay results.

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.

>1 month: 70%-165%

<1 month: Normal, full-term and premature newborn infants may have  mildly decreased levels (> or =30% to 35%) which reach adult levels within 21 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

Acquired deficiencies are much more common than congenital.


Patients that are congenitally deficient homozygous generally have activity levels less than or equal to10% to 20%.


Patients that are congenitally deficient heterozygous generally have activity levels less than or equal to 50%.


Congenital deficiency may occur in combined association with factor VIII deficiency.

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

Factor V (labile factor) is highly susceptible to proteolytic inactivation, with the potential for spuriously decreased assay results. In normal individuals, after freeze-thaw of citrate plasma, factor V activity typically may be 10% to 20% less than observed in a fresh plasma specimen, and in occasional individuals, a more marked decrease of factor V activity occurs. Normal results can be regarded as reliable, but decreased factor V activity results need to be correlated with other clinical and laboratory information. Repeat testing may be necessary.

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. Asselta R, Peyvandi F: Factor V deficiency. Semin Thromb Hemost. 2009 Jun;35(4):382-389

4. Lippi G, Favaloro EJ, Montagnana M, et al: Inherited and acquired factor V deficiency. Blood Coagul Fibrinolysis. 2011;22(3):160-166

5. Spreafico M, Peyvandi F: Combined FV and FVIII deficiency. Haemophilia. 2008 Nov;14(6):1201-1208

6. Kottke-Marchant K, ed: Laboratory Hematology Practice. Wiley Blackwell Publishing; 2012

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