Clotting time

Last updated
Clotting time
Specialty Haematology
MeSH D014914
MedlinePlus 003652

Clotting time is a general term for the time required for a sample of blood to form a clot, or, in medical terms, coagulate. The term "clotting time" is often used when referring to tests such as the prothrombin time (PT), activated partial thromboplastin time (aPTT or PTT), activated clotting time (ACT), thrombin time (TT), or Reptilase time. These tests are coagulation studies performed to assess the natural clotting ability of a sample of blood. In a clinical setting, healthcare providers will order one of these tests to evaluate a patient's blood for any abnormalities in the time it takes for their blood to clot. [1] Each test involves adding a specific substance to the blood and measuring the time until the blood forms fibrin which is one of the first signs of clotted blood. [2] Each test points to a different component of the clotting sequence which is made up of coagulation factors that help form clots. Abnormal results could be due to a number of reasons including, but, not limited to, deficiency in clotting factors, dysfunction of clotting factors, blood-thinning medications, medication side-effects, platelet deficiency, inherited bleeding or clotting disorders, liver disease, or advanced illness resulting in a medical emergency known as disseminated intravascular coagulation (DIC). [3]

Contents

Methods

There are various methods for determining the clotting time, the prototype historical method being the capillary tube method. [4] It is affected by calcium ion levels and many diseases. The normal range of clotting times is 2-8 minutes.

For the measurement of clotting time by the test tube method, blood is placed in a glass test tube and kept at 37°C. The required time for the blood to clot is measured. [5]

There are several other methods, including testing for those on blood thinners, such as heparin or warfarin. Activated partial thromboplastin time (aPTT) is used for heparin studies and the normal range is 20–36 seconds, depending upon which type of activator is used in the study. [6] Prothrombin time (PT) is used for warfarin studies and the normal values differ for men and women. Adult male PT normal range is 9.6–11.8 seconds, while adult females' normal range is 9.5–11.3 seconds. [6] Internationalized normalized ratio (INR) is also a warfarin study, with therapeutic ranges of 2–3 for standard warfarin and 3–4.5 for high-dose warfarin. [6] In a veterinary study of bovine animals, the mean ACT was 145 seconds with a range of 120–180 seconds. Standard deviations were 18 and 13 for the first and second sampling, respectively. Repeatability of the ACT was acceptable. [7]

Related Research Articles

<span class="mw-page-title-main">Thrombus</span> Blood clot

A thrombus, colloquially called a blood clot, is the final product of the blood coagulation step in hemostasis. There are two components to a thrombus: aggregated platelets and red blood cells that form a plug, and a mesh of cross-linked fibrin protein. The substance making up a thrombus is sometimes called cruor. A thrombus is a healthy response to injury intended to stop and prevent further bleeding, but can be harmful in thrombosis, when a clot obstructs blood flow through a healthy blood vessel in the circulatory system.

<span class="mw-page-title-main">Coagulation</span> Process of formation of blood clots

Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The process of coagulation involves activation, adhesion and aggregation of platelets, as well as deposition and maturation of fibrin.

<span class="mw-page-title-main">Disseminated intravascular coagulation</span> Medical condition where blood clots block small blood vessels

Disseminated intravascular coagulation (DIC) is a condition in which blood clots form throughout the body, blocking small blood vessels. Symptoms may include chest pain, shortness of breath, leg pain, problems speaking, or problems moving parts of the body. As clotting factors and platelets are used up, bleeding may occur. This may include blood in the urine, blood in the stool, or bleeding into the skin. Complications may include organ failure.

<span class="mw-page-title-main">Antiphospholipid syndrome</span> Medical condition

Antiphospholipid syndrome, or antiphospholipid antibody syndrome, is an autoimmune, hypercoagulable state caused by antiphospholipid antibodies. APS can lead to blood clots (thrombosis) in both arteries and veins, pregnancy-related complications, and other symptoms like low platelets, kidney disease, heart disease, and rash. Although the exact etiology of APS is still not clear, genetics is believed to play a key role in the development of the disease. Diagnosis is made based on symptoms and testing, but sometimes research criteria are used to aid in diagnosis. The research criteria for definite APS requires one clinical event and two positive blood test results spaced at least three months apart that detect lupus anticoagulant, anti-apolipoprotein antibodies, and/or anti-cardiolipin antibodies.

<span class="mw-page-title-main">Thrombin</span> Enzyme involved in blood coagulation in humans

Prothrombin is encoded in the human by the F2 gene. It is proteolytically cleaved during the clotting process by the prothrombinase enzyme complex to form thrombin.

Low-molecular-weight heparin (LMWH) is a class of anticoagulant medications. They are used in the prevention of blood clots and, in the treatment of venous thromboembolism, and the treatment of myocardial infarction.

<span class="mw-page-title-main">Prothrombin time</span> Blood test that evaluates clotting

The prothrombin time (PT) – along with its derived measures of prothrombin ratio (PR) and international normalized ratio (INR) – is an assay for evaluating the extrinsic pathway and common pathway of coagulation. This blood test is also called protime INR and PT/INR. They are used to determine the clotting tendency of blood, in such things as the measure of warfarin dosage, liver damage, and vitamin K status. PT measures the following coagulation factors: I (fibrinogen), II (prothrombin), V (proaccelerin), VII (proconvertin), and X.

<span class="mw-page-title-main">Bleeding diathesis</span> Medical condition

In medicine (hematology), bleeding diathesis is an unusual susceptibility to bleed (hemorrhage) mostly due to hypocoagulability, in turn caused by a coagulopathy. Therefore, this may result in the reduction of platelets being produced and leads to excessive bleeding. Several types of coagulopathy are distinguished, ranging from mild to lethal. Coagulopathy can be caused by thinning of the skin, such that the skin is weakened and is bruised easily and frequently without any trauma or injury to the body. Also, coagulopathy can be contributed by impaired wound healing or impaired clot formation.

<span class="mw-page-title-main">Partial thromboplastin time</span> Test for coagulation of blood

The partial thromboplastin time (PTT), also known as the activated partial thromboplastin time, is a blood test that characterizes coagulation of the blood. A historical name for this measure is the kaolin-cephalin clotting time (KCCT), reflecting kaolin and cephalin as materials historically used in the test. Apart from detecting abnormalities in blood clotting, partial thromboplastin time is also used to monitor the treatment effect of heparin, a widely prescribed drug that reduces blood's tendency to clot.

Mixing studies are tests performed on blood plasma of patients or test subjects to distinguish factor deficiencies from factor inhibitors, such as lupus anticoagulant, or specific factor inhibitors, such as antibodies directed against factor VIII. Mixing studies are screening tests widely performed in coagulation laboratories. The basic purpose of these tests is to determine the cause of prolongation of Prothrombin Time (PT), Partial Thromboplastin Time, or sometimes of thrombin time (TT). Mixing studies take advantage of the fact that factor levels that are 50 percent of normal should give a normal Prothrombin time (PT) or Partial thromboplastin time (PTT) result. Factor deficient plasmas are used in mixing studies. Plasma with known factor deficiencies are commercially available but are very expensive, so they are often prepared in the laboratory and can then be used for mixing tests.

Lupus anticoagulant is an immunoglobulin that binds to phospholipids and proteins associated with the cell membrane. Its name is a partial misnomer, as it is actually a prothrombotic antibody in vivo. The name derives from their properties in vitro, as these antibodies increase coagulation times in laboratory tests such as the activated partial thromboplastin time (aPTT). Investigators speculate that the antibodies interfere with phospholipids used to induce in vitro coagulation. In vivo, the antibodies are thought to interact with platelet membrane phospholipids, increasing adhesion and aggregation of platelets, which accounts for the in vivo prothrombotic characteristics.

Thromboelastography (TEG) is a method of testing the efficiency of blood coagulation. It is a test mainly used in surgery and anesthesiology, although increasingly used in resuscitations in emergency departments, intensive care units, and labor and delivery suites. More common tests of blood coagulation include prothrombin time (PT) and partial thromboplastin time (aPTT) which measure coagulation factor function, but TEG also can assess platelet function, clot strength, and fibrinolysis which these other tests cannot.

<span class="mw-page-title-main">Hypoprothrombinemia</span> Medical condition

Hypoprothrombinemia is a rare blood disorder in which a deficiency in immunoreactive prothrombin, produced in the liver, results in an impaired blood clotting reaction, leading to an increased physiological risk for spontaneous bleeding. This condition can be observed in the gastrointestinal system, cranial vault, and superficial integumentary system, affecting both the male and female population. Prothrombin is a critical protein that is involved in the process of hemostasis, as well as illustrating procoagulant activities. This condition is characterized as an autosomal recessive inheritance congenital coagulation disorder affecting 1 per 2,000,000 of the population, worldwide, but is also attributed as acquired.

<span class="mw-page-title-main">Thrombin time</span>

The thrombin time (TT), also known as the thrombin clotting time (TCT), is a blood test that measures the time it takes for a clot to form in the plasma of a blood sample containing anticoagulant, after an excess of thrombin has been added. It is used to diagnose blood coagulation disorders and to assess the effectiveness of fibrinolytic therapy. This test is repeated with pooled plasma from normal patients. The difference in time between the test and the 'normal' indicates an abnormality in the conversion of fibrinogen to fibrin, an insoluble protein.

Ecarin is an enzyme that is derived from the venom of the Indian saw-scaled viper, Echis carinatus, It is the primary reagent in the Ecarin clotting time test.

A coagulation screen is a combination of screening laboratory tests, designed to provide rapid non-specific information, which allows an initial broad categorization of haemostatic problems.

The fibrinolysis system is responsible for removing blood clots. Hyperfibrinolysis describes a situation with markedly enhanced fibrinolytic activity, resulting in increased, sometimes catastrophic bleeding. Hyperfibrinolysis can be caused by acquired or congenital reasons. Among the congenital conditions for hyperfibrinolysis, deficiency of alpha-2-antiplasmin or plasminogen activator inhibitor type 1 (PAI-1) are very rare. The affected individuals show a hemophilia-like bleeding phenotype. Acquired hyperfibrinolysis is found in liver disease, in patients with severe trauma, during major surgical procedures, and other conditions. A special situation with temporarily enhanced fibrinolysis is thrombolytic therapy with drugs which activate plasminogen, e.g. for use in acute ischemic events or in patients with stroke. In patients with severe trauma, hyperfibrinolysis is associated with poor outcome. Moreover, hyperfibrinolysis may be associated with blood brain barrier impairment, a plasmin-dependent effect due to an increased generation of bradykinin.

Thromboelastometry (TEM), previously named rotational thromboelastography (ROTEG) or rotational thromboelastometry (ROTEM), is an established viscoelastic method for hemostasis testing in whole blood. It is a modification of traditional thromboelastography (TEG).

Activated clotting time (ACT), also known as activated coagulation time, is a test of coagulation.

Blood clotting tests are the tests used for diagnostics of the hemostasis system. Coagulometer is the medical laboratory analyzer used for testing of the hemostasis system. Modern coagulometers realize different methods of activation and observation of development of blood clots in blood or in blood plasma.

References

  1. ↑ Epstein KL (January 2015). "Chapter 119 - Evaluation of Hemostasis". In Sprayberry KA, Robinson NE (eds.). Robinson's Current Therapy in Equine Medicine (Seventh ed.). St. Louis: W.B. Saunders. pp. 500–502. doi:10.1016/b978-1-4557-4555-5.00119-9. ISBN   978-1-4557-4555-5.
  2. ↑ Weisel JW, Litvinov RI (March 2013). "Mechanisms of fibrin polymerization and clinical implications". Blood. 121 (10): 1712–1719. doi:10.1182/blood-2012-09-306639. PMC   3591795 . PMID   23305734.
  3. ↑ Yang R, Moosavi L (2023). "Prothrombin Time". StatPearls. Treasure Island (FL): StatPearls Publishing. PMID   31334989 . Retrieved 2023-11-08.
  4. ↑ Lewis, RC; Glueck, HI (August 1958). "A micromethod for determining clotting time, using capillary blood and siliconized tubes". The Journal of laboratory and clinical medicine. 52 (2): 299–303. PMID   13564008.
  5. ↑ Dg D (2016). "Bleeding Time (BT) and Clotting Time (CT)". BioScience. ISSN   2521-5760 . Retrieved 2017-10-26.
  6. 1 2 3 Silvestri LA (2014). Saunders comprehensive review for the NCLEX-RN examination. pp. 116–117. ISBN   978-1-4557-3752-9. OCLC   1280839582.
  7. ↑ Riley JH, Lassen ED (1979). "Activated coagulation times of normal cows". Veterinary Clinical Pathology. 8 (1): 31–33. doi:10.1111/j.1939-165x.1979.tb00879.x. PMID   15314780.
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