Blood Coagulation Factors

• There is a cascade of coagulation factors needed for proper coagulation.
• The following diagram shows the role of each coagulation factor.

Blood coagulation process: Coagulation pathways

Blood coagulation factors:

What are the 13 coagulation factors in the body?

1. Fibrinogen (Factor 1).
2. Prothrombin (Factor II).
3. Thromboplastin (Factor III).
4. Ionized Calcium (Factor IV).
5. Proaccelerin (Factor V).
6. Factor VI.
7. Proconvertin (Factor VII).
8. Antihemophilic factor (Factor VIII).
9. Chrismats factor (Factor IX).
10. Stuart factor (Factor X).
11. Plasma thromboplastin antecedent (Factor XI).
12. Hageman’s factor (Factor XII).
13. Fibrin-stabilizing factor (Factor XIII).

Fibrinogen, Factor I:

1. Fibrinogen is a complex protein and polypeptide, and it has an enzymatic property where it is converted into fibrin.
   1. Fibrin and platelets form the blood clot to stop the bleeding.
2. Fibrinogen is necessary for the clotting mechanism. 
   1. Fibrinogen is a globulin protein.
   2. Fibrinogen is produced by the liver and is also called acute-phase protein.
   3. It is raised in acute inflammation and necrosis.
3. This is the precursor of Fibrin.
   1. Fibrinogen  (factor I) converts to Fibrin.
   2. It is part of the common pathway.
4. When exposed to thrombin, fibrinogen splits into fibrin and forms a polymerized clot.
5. Fibrinogen deficiency may be:
   1. Afibrinogenemia.
   2. Hypofibrogenemia.
   3. Dysfibrogenemia.

Synthesis of fibrinogen and its role in forming a fibrin clot

Fibrinogen metabolism

1. Increased level of fibrinogen is associated with:
   1. increased risk of coronary heart disease.
   2. Stroke (various cerebral accidents and diseases).
   3. Acute myocardial infarction.
   4. Peripheral arterial disease.
   5. Nephrotic syndrome.
   6. Pregnancy (eclampsia).
   7. Cancers.
   8. Multiple myeloma and Hodgkin’s lymphoma.
2. Decreased level of the fibrinogen level is seen in:
   1. Liver diseases.
   2. Malnutrition.
   3. DIC (disseminated intravascular coagulopathy).
   4. Cancers.
   5. Dysfibrinogenemia.
   6. Primary fibrinolysis.
   7. Hereditary and congenital hypofibrinogenemia.
3. Precautions for fibrinogen level estimation:
   1. Blood transfusion in the last month will affect the result.
   2. A diet containing omega-3 and omega-6 fatty acids reduces the fibrinogen level.
   3. Estrogen and oral contraceptives also increase the fibrinogen level.
   4. Anabolic agents, phenobarbitol, streptokinase, and valproic acid reduce the level of fibrinogen.
   5. A high level of heparin interferes with test results.
4. Normal fibrinogen level:
   1. Adult = 200 to 400 mg/dL (2.0 to 4.0 g/L)
   2. Newborn = 125 to 300 mg/dL
      1. Critical value = <100 mg/dL
5. Panic values:
   1. <50 mg/dL (<0.5 g/L) can lead to hemorrhage after traumatic surgery.
   2. >700 mg/dL (7.0 g/L) level is a risk for coronary artery disease and cerebrovascular disease.

Prothrombin, Factor II:

1. Prothrombin is a glycoprotein with a molecular weight of 71,600 daltons in the blood and plasma.
   1. Prothrombin is a vitamin K-dependent clotting factor.
   2. This is produced in the liver. and needs vitamin K for its production.
   3. It is most abundant and has the longest half-life of the vitamin K-dependent clotting factors.
   4. It takes about 3 weeks before the body stores vitamin K are exhausted.
2.  Prothrombin is converted to thrombin, which stimulates platelet aggregation and activates cofactors (factor X or prothrombinase), Factor C, and Factor XIII.
3. Deficiency of prothrombin:
   1. The deficiency of prothrombin will delay thrombin formation, leading to hemorrhagic symptoms.
   2. Hypoprothrombinemia:
      1. It is autosomal recessive inheritance.
      2. This may be acquired by vitamin K deficiency or oral anticoagulants like warfarin therapy.
      3. S/S depends upon the level of prothrombin level.
         1. These patients may have H/O epistaxis, menorrhagia, post-partum hemorrhage, and hemorrhage after the surgery.
         2. Hemorrhages may occur after broad-spectrum antibiotic therapy.
         3. Prothrombin level is <2% to <50% of normal.
      4. It is a rare condition, and it may lead to hemorrhagic symptoms.
      5. PTT and PT are prolonged and have normal thrombin times.
      6. A definitive diagnosis depends upon the prothrombin (functional activity) assay or the prothrombin level antigenic concentration.

Thromboplastin, Factor III, or Tissue factor:

1. Tissue thromboplastin is composed of phospholipids and lipoproteins and can be extracted from various tissues.
2. Thromboplastin is generated by the extrinsic and intrinsic pathways.
3. Thromboplastin is an enzyme that is released from damaged cells, particularly from the platelets.
   1. This is found in the brain, lungs, and other tissues. It is also present in the platelets.
4. Mode of action:
   1. This is a tissue factor that will activate VII when blood is exposed to tissue fluid.
   2. Tissue thromboplastin forms the complex with factor VII, Ca⁺⁺, and stimulates the extrinsic coagulation pathway.
   3. The above complex was used as a reagent for the PT test.
   4. It converts prothrombin to thrombin.

Role of thromboplastin in coagulation

Ionized Calcium Factor IV:

1. Ionized calcium is important for the clotting system.
2. Calcium is necessary as a cofactor in several steps of the coagulation pathways.

1. The functions of ionized calcium:
2. Ionized calcium is needed in the clotting system at the following stages:
   1. This active form of Calcium is needed to activate thromboplastin.
   2. Convert Prothrombin to Thrombin.
   3. Activate factor XIII to  XIIIa.
   4.  Activate factor X to  Xa.
   5. For the formation of fibrin.

1. Of calcium in the blood, 50% is ionized, and a very small amount is needed in the clotting mechanism.

Proaccelerin, Factor V:

1. It is also called a labile factor.
2. This is a globulin and is labile in the plasma. It is not found in the serum.
3. This is synthesized in the liver; its molecular weight is 350,000 daltons, has a short half-life, and is heat-labile.
4. It is present in the α-granules of the platelets.
5. This is not vitamin K-dependent.
6. Stability of factor V:
   1. Factor V is unstable and is reduced in 2 to 3 days when the blood is refrigerated in the blood bank.
   2. Refrigeration preserves factor V in laboratory plasma, but even at 4°C, factor V is reduced within 24 hours.
   3. Freezing the specimen immediately is important to preserve factor V activity.

Calcium’s role in coagulation

The functions of factor V:

1. It is consumed during clotting and accelerates the transformation of prothrombin to thrombin.
2. In the presence of factor VIII, it helps the normal coagulation process.
3. This will deteriorate rapidly in the oxalate plasma and is slightly slow in the citrated plasma.
4. This is consumed in the clotting process and not found in the serum.
5. This helps as a cofactor to transfer prothrombin to thrombin.
6. Congenital deficiency of Factor V is called parahemophilia.

Factor V deficiency leads to:

1. Ecchymosis.
2. Epistaxis.
3. Gingival bleeding.
4. Gastrointestinal bleeding.
5. CNS bleeding.
6. Umbilical bleeding.
7. Menorrhagia.
8. Acquired deficiency of factor V is seen in the case of antibodies and is also associated with liver disease, carcinoma, tuberculosis, and DIC.
9. Bleeding tendency is seen when this is <10%, where the normal value is 50 to 150% of normal.
   1. PT and APTT are prolonged in factor V deficiency.
   2. APTT may be normal in mild deficiency and abnormal in severe deficiency.
   3. Thrombin time is normal.
10. Treatment: These patients are treated with fresh or frozen plasma.
    1. Cryoprecipitate does not contain an adequate amount of factor V.

Role of snake venom in coagulation

Factor VI:

• This factor does not exist.

Proconvertin, Factor VII (Stable factor):

1. This factor is synthesized in the liver and depends on vitamin K for its activity.
2. This is beta-globulin with a molecular weight of 50,000 daltons.
   1. This has a half-life of 4 to 6 hours and is produced in the liver.
   2. This is a vitamin K-dependent factor.
3. This factor is not destroyed or consumed during the clotting process, so it is found in the serum and in the plasma.
4.  This factor is activated by thromboplastin.
5. Functions of Factor VII:
   1. The division of the coagulation system into intrinsic and extrinsic pathways is not found in vivo because activated factor VIIa can activate factors IX and X.
   2. Thromboplastin activates factor X.
   3. Its activity increases by the factor XIIa and IXa.
   4. Factor VII needs tissue factor, thrombin, and Ca⁺⁺, to become VIIa.
6. The deficiency of factor VII is very rare.
   1. This may be seen in liver diseases.
      1. Warfarin therapy.
      2. Dietary vitamin K deficiency.
7. S/S of factor VII deficiency:
   1. These patients develop deep muscle hematoma.
   2. These patients may have a joint hemorrhage.
   3. There may be epistaxis.
   4. There may be menorrhagia.
8. Diagnosis of factor VII deficiency:
   1. PT is prolonged.
   2. APTT is normal (factor VII is not measured in this test).
   3. Bleeding time is normal.
   4. Diagnosis of factor VII deficiency needs a one-stage factor assay.
   5. Patients with <1% activity may have severe bleeding manifestations (normal factor VII value is 65 to 140% of normal).
9. Treatment is needed with fresh frozen plasma.
   1. Vitamin K supplementation.
   2. Prothrombin complex concentrates.

Blood Coagulation Factors: Factor VII function

Factor VII deficiency:

Antihemophilic factor, Factor VIII:

1. This factor VIII was called antihemophilic globulin and is now called factor VIII (anti-hemophilic factor).
2. This factor is produced by the liver’s sinusoidal and endothelial cells.
   1. This is a glycoprotein with a molecular weight of 330,000 daltons and is a very important factor.
3. Synthesis of factor VIII:
   1. Its synthesis site is unclear, but the idea is that it may be liver.
   2. Severe liver failure does not lead to its deficiency.
   3. It is considered that cells present in different organs like fibroblasts, lymphocytes, macrophages, and vascular endothelial cells may be a source.
4. von Willibrand’s factor:
   1. Factor VIII is present in the plasma, is a complex with von Willebrand’s factor, and circulates in plasma.
   2. von Willibrand’s factor is a glycoprotein and is synthesized by the megakaryocytes and endothelial cells.
   3. It circulates with factor VIII as FVIII+vWF.
   4. 1% to 2% of the complex function as procoagulant (FVIII: C) can be measured by clotting assay, and the rest of the portion is FVIII: vWF; this will mediate platelets adhesion.
5. This is a very labile factor.
   1. After the blood transfusion, 50% of the activity is lost in 8 to 12 hours.
   2. It is stable in the fresh frozen plasma.
   3. The lyophilization process will preserve its activity with a very small loss of it.
6. Hemophilia is characterized by the deficiency of this factor VIII.
7. This factor is consumed during clotting, so it is not found in the serum.
8. This factor has different fractions, and these are divided based on molecular weight.
   1. High molecular weight type.
   2. A low molecular weight type.
   3. In hemophilia, classical factor VIII deficiency is deficient in the low molecular weight molecule, and the high molecular weight molecule is normal.
9. Functions of Factor VIII:
   1. FVIII: C has a half-life of 8 to 12 hours, and it acts as a cofactor.
   2. This cofactor accelerates the conversion of factor X to Xa.
   3. The above cofactor converts X to Xa in the presence of factor IXa + calcium and phospholipids complex.

1. 4. Factor VIII is also an acute-phase protein. It will be increased in:
      1. Inflammation.
      2. Pregnancy.
      3. Stress.
      4. Infections.

Christmas  factor, Factor IX:

1. This is a stable protein factor. This is a single-chain glycoprotein with a molecular weight of 60,000 daltons.
   1. This is synthesized in the liver and is vitamin K-dependent.
   2. This takes part in the intrinsic pathway, where it is activated by XIa in the presence of Ca⁺⁺.
2. This is not consumed during the clotting process.
   1. It has a half-life of 20 hours.
   2. This is also not consumed by aging and is present in the serum and plasma.
   3. There is no significant loss of storing blood or plasma at 4 °C for 2 weeks.
3. This is also called antihemophilic factor B or Christmas factor.
4. This is an essential component of the intrinsic thromboplastin generation system.
5. This helps factor Va + factor VIIIa lead to their amplification.

Stuart-Prower factor, Factor X:

1. This is alpha globulin with a molecular weight of 58,800 daltons.
   1. It comprises light and heavy chains held together by a single disulfide bond.
   2. It requires Vitamin K for its synthesis in the liver and is released into plasma as a precursor to serine protease.
   3. Activation of factor X to Xa involves the cleavage of a peptide bond in the heavy chain.
      1. This reaction in the intrinsic pathway occurs in the presence of factor VIIIa, calcium ions, and phospholipids.
      2. The same bond is cleaved by factor VIIa in the presence of tissue factor in the extrinsic pathway.
   4. Its half-life is roughly 40 hours.
2. This is also called thrombokinase.
3. This is a relatively stable factor and is not consumed in the clotting process.
   1. This is found in serum and plasma.
   2. Factor Xa is inactivated by a serine protease inhibitor.
4. This factor helps to convert prothrombin to thrombin.

1. Deficiency of factor X:
   1. Inherited deficiency of factor X is extremely rare. Its transmission is autosomal recessive.
   2. Factor X deficiency may occur at any age, but the symptoms are common at a very young age.
2. S/S of factor X deficiency:
   1. Bleeding sites vary according to the severity of the deficiency.
   2. There may be easy bruising.
   3. There may be epistaxis.
   4. There is gastrointestinal bleeding.
   5. There is menorrhagia.
   6. In mild cases, you may see hemarthrosis.
   7. There may be a hemorrhage in the CNS.
   8. There is severe bleeding in the post-operative stage.
   9. factor X deficiency was reported in amyloidosis cases.
3. Diagnosis of factor X deficiency:
   1. Take family history and laboratory data.
   2. Workup for liver diseases and vitamin K deficiency.

Treatment of factor X deficiency:

1. It consists of fresh frozen plasma.
2. Or can be treated with prothrombin-complex concentrate.
3. If the deficiency is dietary, vitamin K will help to treat these cases.

Plasma thromboplastin antecedent, Factor XI:

1. This is beta-globulin (glycoprotein). Its molecular weight is 143,000 daltons.
   1. It is synthesized in the liver and secreted into plasma.
   2. It consists of two polypeptide chains linked by single disulfide bonds.
2. This is also called antihemophilic factor C.
3. This is partially consumed during clotting.
   1. This is found in the serum.
   2. Half-life a few hours.
4. This is needed in the intrinsic pathway to form the thromboplastin generation cascade.
5. Factor XI and factor XII are “contact factors” for clotting.
   1. When it contacts the negatively charged surface, factor XI is activated by factor XIIa.

Hageman’s factor, Factor XII : 

1. This is single-chain β-globulin with a molecular weight of 76,000 daltons.
   1. It is believed to be synthesized by the liver and circulated in the blood circulation as an inactive zymogen.
2. Mode of action of factor XII:
   1. This is not consumed during clotting.
   2. Hageman factor + glass contact converted from the inactive active form.
   3. In vitro: This is a surface contact factor. After contact with a negatively charged surface in vitro, like glass, kaolin, celite, or ellagic acid, it causes autoactivation of this factor XII to XIIa. This is also converted into serine protease.
   4. This process takes place in the intrinsic pathway of coagulation.
   5. This is activated by collagen.
   6. In vivo, factor XII activation occurs by contact with the cell membrane and components of white blood cells (polys).
3. Factor XII exposes an active site that will convert prekallikrein to kallikrein and activates factor XI.
4. A small amount of activated factor XIIa activates its substrates: prekallikrein, factor XI, and HMWK.
5. Deficiency of factor XII:
   1. It is known as the Hageman trait and is inherited in an autosomal-recessive manner.
   2. It is not associated with clinical bleeding or hemorrhage.
   3. There are chances for thrombotic diseases like myocardial infarction or thromboembolism.
   4. These patients are asymptomatic, and there is no surgical risk for hemorrhage.
6. Diagnosis of factor XII deficiency:
   1. PT level is normal.
   2. APTT  is prolonged.
      1. APTT is corrected by mixing with pooled normal plasma, aged serum, or adsorbed plasma.
   3. Factor XII assay shows decreased or absent levels, confirming the diagnosis.
7. Precaution for the collection of the blood:
   1. Avoid contact activation during blood collection.
   2. Take the blood in the plastic syringe and transfer it to siliconized anticoagulated test tubes.
   3. Avoid freezing or thawing.
   4. Perform the test in fresh plasma.

Fibrin-stabilizing factor (Fibrinase), Factor XIII:

1.  Factor XIII’s molecular weight is 320,000 daltons, and it circulates with fibrinogen.
   1. Factor XIII has two subunits:
      1. α2-chain is found in various tissues and cells like platelets, placenta, prostate, and macrophagic cells.
      2. β2-subunit is synthesized in the liver and circulates in the blood circulation as a free dimer.
         1. It is postulated that the β2-subunit helps in the stabilization of the α2-subunit.
         2. The function of the β2-subunit is still not clear.
2. This factor acts in the presence of Calcium.
3. This is a serum factor.
   1. Adding Ca⁺⁺ and serum factor (Factor XIII) gives rise to coarse fibrin clot formation.
   2. This stabilizes polymerized fibrin monomer in the initial stage of clot formation.

1. Mode of action of factor XIII:
2. In the final stage of the coagulation process, there are:
   1. Generation of thrombin.
   2. Polymerization of the fibrin.
   3. Activation of factor XIII, which is responsible for stable fibrin clot.
   4. Factor XIII is a proenzyme for plasma transglutaminase.
   5. In the presence of fibrin, thrombin converts Factor XIII to an enzyme called factor XIIIa.
3. Functions of Factor XIII:
   1. It stabilizes the fibrin clot.
   2. It acts as a catalyst, forming a bond between various proteins like:
      1. Fibrin monomer.
      2. Fibronectin.
      3. Collagenase.
      4. α2-plasmin inhibitor.

1. 3. 3. This cross-linking of various proteins leads to:
         1. Hemostasis.
         2. Maintenance of pregnancy.
         3. Wound healing.
2. Deficiency of factor XIII:
   1. It may be a congenital deficiency as an autosomal recessive trait.
   2. It may also be a homozygous deficiency.
3. S/S of factor XIII deficiency:
   1. In homozygous cases, there are moderate to severe attacks of hemorrhage.
   2. In typical cases, there is an initial stoppage of the bleeding followed by a recurrence of the bleeding after 36 hours or more after the initial trauma.
   3. This repeated episode of bleeding is due to the dissolution of the fibrin clot and later on not stabilized by factor XIII.
   4. At birth, there is bleeding from the umbilicus.
   5. Acquired partial deficiency of factor XIII is seen in leukemias, severe liver disease, and DIC cases.

4. Diagnosis of factor XIII deficiency:
   1. PT, APTT, fibrinogen level, bleeding time (BT), and platelet counts are normal.
   2. Screening test for factor XIII deficiency:
      1. Solubility of a recalcified plasma clot in a 5-molar urea solution. The clot will dissolve within 24 hours.

Normal values of clotting factors:

Questions and answers: