Thromboplastin
Encyclopedia
Thromboplastin is a plasma
protein
aiding blood coagulation through conversion of prothrombin to thrombin.
Although sometimes used as a synonym for tissue factor
, this is a misconception. Historically, thromboplastin was a lab reagent
, usually derived from placental
sources, used to assay prothrombin times (PT time). Thromboplastin, by itself, could activate the extrinsic coagulation pathway. When manipulated in the laboratory, a derivative could be created called partial thromboplastin. Partial thromboplastin was used to measure the intrinsic pathway. This test is called the aPTT, or activated partial thromboplastin time
. It was not until much later that the subcomponents of thromboplastin and partial thromboplastin were identified. Thromboplastin is the combination of both phospholipids and tissue factor, both needed in the activation of the extrinsic pathway. However, partial thromboplastin is just phospholipids, and not tissue factor.
Currently, recombinant tissue factor is available and used in some PT assays. Placental derivatives are still available and used in some laboratories. Phospholipid is available as an independent reagent or in combination with tissue factor as thromboplastin. Complete thromboplastin consists of tissue factor, phospholipids (since platelets were removed from blood sample being tested), and CaCl2
to reintroduce calcium ions that were chelated by sodium citrate originally used to prevent coagulation of the sample blood during transportation and/or storage.
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
aiding blood coagulation through conversion of prothrombin to thrombin.
Although sometimes used as a synonym for tissue factor
Tissue factor
Tissue factor, also called platelet tissue factor, factor III, thrombokinase, or CD142 is a protein present in subendothelial tissue, platelets, and leukocytes necessary for the initiation of thrombin formation from the zymogen prothrombin. An incorrect synonym is thromboplastin...
, this is a misconception. Historically, thromboplastin was a lab reagent
Reagent
A reagent is a "substance or compound that is added to a system in order to bring about a chemical reaction, or added to see if a reaction occurs." Although the terms reactant and reagent are often used interchangeably, a reactant is less specifically a "substance that is consumed in the course of...
, usually derived from placental
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...
sources, used to assay prothrombin times (PT time). Thromboplastin, by itself, could activate the extrinsic coagulation pathway. When manipulated in the laboratory, a derivative could be created called partial thromboplastin. Partial thromboplastin was used to measure the intrinsic pathway. This test is called the aPTT, or activated partial thromboplastin time
Partial thromboplastin time
The partial thromboplastin time or activated partial thromboplastin time is a performance indicator measuring the efficacy of both the "intrinsic" and the common coagulation pathways...
. It was not until much later that the subcomponents of thromboplastin and partial thromboplastin were identified. Thromboplastin is the combination of both phospholipids and tissue factor, both needed in the activation of the extrinsic pathway. However, partial thromboplastin is just phospholipids, and not tissue factor.
Currently, recombinant tissue factor is available and used in some PT assays. Placental derivatives are still available and used in some laboratories. Phospholipid is available as an independent reagent or in combination with tissue factor as thromboplastin. Complete thromboplastin consists of tissue factor, phospholipids (since platelets were removed from blood sample being tested), and CaCl2
Calcium chloride
Calcium chloride, CaCl2, is a salt of calcium and chlorine. It behaves as a typical ionic halide, and is solid at room temperature. Common applications include brine for refrigeration plants, ice and dust control on roads, and desiccation...
to reintroduce calcium ions that were chelated by sodium citrate originally used to prevent coagulation of the sample blood during transportation and/or storage.