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Encyclopedia > Partial thromboplastin time

The partial thromboplastin time (PTT) or activated partial thromboplastin time (aPTT or APTT) is a performance indicator measuring the efficacy of both the intrinsic and the common coagulation pathways. Apart from detecting abnormalities in blood clotting, it is also used to monitor the treatment effects with heparin, a major anticoagulant. The coagulation of blood is a complex process during which blood forms solid clots. ... Heparin is a highly sulfated glycosaminoglycan widely used as an injectable anticoagulant. ... An anticoagulant is a substance that prevents coagulation; that is, it stops blood from clotting. ...


Methodology

Blood is collected, by a phlebotomist, with oxalate which arrests coagulation by binding calcium. This specimen is delivered to the laboratory. In order to activate the intrinsic pathway, phospholipid, an activator (such as silica, celite, kaolin, ellagic acid), and calcium (to reverse the anticoagulant effect of the oxalate) are mixed into the plasma sample . The time is measured until a thrombus (clot) forms. This testing is performed by a Medical technologist. A phlebotomist is an individual trained to draw blood (venipuncture), either for laboratory tests, or for blood donations. ... An oxalate (called also: ethanedioate) is a salt or ester of oxalic acid. ... Two schematic representations of a phospholipid. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... Diatomaceous earth, also known as diatomite, kieselguhr, kieselgur, and Celite, is a naturally occurring, soft, chalk-like, sedimentary rock mineral that is easily crumbled into a fine white to off-white powder. ... Kaolin Kaolinite (Aluminium Silicate Hydroxide) Kaolinite is a mineral with the chemical composition Al2Si2O5(OH)4. ... Ellagic acid C14 H6 O8 CAS No. ... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Atomic mass 40. ... Blood plasma is the liquid component of blood, in which the blood cells are suspended. ... A thrombus, or blood clot, is the final product of the blood coagulation step in hemostasis. ... A Medical Technologist (MT) is an Allied Health Professional who does clinical analysis on human body fluids and performs other types of medical testing. ...


The test is termed "partial" due to the absence of tissue factor from the reaction mixture. Thromboplastin is a substance present in tissues, platelets, and leukocytes necessary for the coagulation of blood; in the presence of calcium ions thromboplastin is necessary for the conversion of prothrombin to thrombin, an important step in coagulation of blood. ...


Interpretation

Values below 25 seconds and over 39 s (depending on local normal ranges) are generally abnormal. Shortening of the PTT has little clinical relevance, as most thrombosis patients have normal coagulation studies. Prolonged APTT may indicate: Look up second in Wiktionary, the free dictionary. ... Thrombosis is the formation of a clot or thrombus inside a blood vessel, obstructing the flow of blood through the circulatory system. ...

To distinguish the above causes, mixing studies are performed, in which the patient's plasma is mixed (initially at a 50:50 dilution) with normal plasma. If the abnormality does not disappear, the sample is said to contain an "inhibitor" (either heparin, antiphospholipid antibodies or coagulation factor specific inhibitors), while if it does correct a factor deficiency is more likely. Deficiencies of factors VIII, IX, XI and XII and rarely von Willebrand factor (if causing a low factor VIII level) may lead to a prolonged aPTT correcting on mixing studies. Heparin is a highly sulfated glycosaminoglycan widely used as an injectable anticoagulant. ... Antiphospholipid syndrome, or antiphospholipid antibody syndrome, is a disorder of coagulation, and causes thrombosis in both arteries and veins, as well as recurrent miscarriage. ... Lupus anticoagulant is an autoimmune disorder caused by antibodies that bind to phospholipids and proteins associated with the cell membrane. ... Haemophilia or hemophilia is the name of any of several hereditary genetic illnesses that impair the bodys ability to control bleeding. ... Factor VIII (FVIII) is an essential clotting factor. ... Factor IX (or Christmas factor or Christmas-Eve factor) is one of the serine proteases (EC 3. ... Factor XI or plasma thromboplastin antecent is one of the enzymes ( EC 3. ... The Hageman factor, is a plasma protein now usually known as factor XII. It is part of the coagulation cascade and activates factor XI and prekallikrein. ... Von Willebrand factor is a blood glycoprotein of the coagulation system. ...


  Results from FactBites:
 
Partial thromboplastin time - Wikipedia, the free encyclopedia (322 words)
The partial thromboplastin time (PTT) or activated partial thromboplastin time (aPTT or APTT) is a performance indicator measuring the efficacy of both the intrinsic and the common coagulation pathways.
The time is measured until a thrombus (clot) forms.
The test is termed "partial" due to the absence of tissue factor from the reaction mixture.
Partial thromboplastin time Encyclopedia of Medicine - Find Articles (903 words)
Measuring the partial thromboplastin time helps to assess which specific clotting factors may be missing or defective.
The PTT test allows a doctor to check that there is enough heparin in the blood to prevent clotting, but not so much as to cause bleeding.
The partial thromboplastin time is the time it takes for a clot to form, measured in seconds.
  More results at FactBites »

 
 

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