Method of Collection:
Sodium Citrate Vacutainer (According To Instructions On Vacutainer)
Days for reporting:
Why is the Test Done?
The PTT is used primarily to investigate unexplained bleeding or clotting. It is ordered along with a prothrombin time (PT) test to evaluate hemostasis, the process that the body uses to form blood clots to help stop bleeding. These tests are usually the starting points for investigating excessive bleeding or clotting disorders.Several proteins called coagulation factors are involved in hemostasis and the formation of blood clots. When an injury occurs and bleeding begins, some coagulation factors are activated in a sequence of steps (coagulation cascade) that eventually help to form a clot. The PTT is used to evaluate the coagulation factors XII, XI, IX, VIII, X, V, II (prothrombin), and I (fibrinogen) as well as prekallikrein (PK) and high molecular weight kininogen (HK). A PT test evaluates the coagulation factors VII, X, V, II, and I (fibrinogen). By evaluating the results of the two tests together, on a can gain clues as to what bleeding or clotting disorder may be present. The PTT and PT are not diagnostic but usually provide information on whether further tests may be needed. PTT is also used it detect nonspecific autoantibodies, such as lupus anticoagulant these are associated with clotting episodes and with recurrent miscarriages. For this reason, PTT testing may be performed as part of a clotting disorder panel to help investigate recurrent miscarriages or diagnose antiphospholipid syndrome (APS). A variation of the PTT called the LA-sensitive PTT may be used for this purpose.� To monitor standard (unfractionated, UF) heparin anticoagulant therapy heparin is an anticoagulation drug that is given intravenously (IV) or by injection to prevent and to treat blood clots (embolism and thromboembolism). It prolongs PTT. When heparin is administered for therapeutic purposes, it must be closely monitored. If too much is given, the treated person may bleed excessively with too little, the treated person may continue to clot. � Based on carefully obtained patient histories, the PTT and PT tests are sometimes selectively performed as pre-surgical or before other invasive procedures to screen for potential bleeding tendencies. � PTT results are typically reported in seconds. A PTT result that falls within a laboratory's reference interval usually indicates normal clotting function. However, mild to moderate deficiencies of a single coagulation factor may be present. The PTT may not be prolonged until the factor levels have decreased to 30% to 40% of normal. Also lupus anticoagulant may be present but may not prolong the PTT result. If the lupus anticoagulant (LA) is suspected, a more sensitive LA-sensitive PTT or a dilute Russell viper venom time (DRVVT) can be used to test for it.Prolonged Normal Liver disease, decreased vitamin K, decreased or defective factor VII Normal Prolonged Hemophilia A or B (decreased or defective factor VIII or IX) or factor XI deficiency, von Willebrand disease, factor XII deficiency, or lupus anticoagulant present Prolonged Prolonged Decreased or defective factor I (fibrinogen), II (prothrombin), V or X, severe liver disease, disseminated intravascular coagulation (DIC) Normal Normal or slightly prolonged May indicate normal hemostasis; however PT and PTT can be normal in conditions such as mild deficiencies in other factors and mild form of von Willebrand disease. Further testing may be required to diagnose these conditions. Shortened PTT tests may be due to � Disseminated intravascular coagulation (DIC)�in the early stages of DIC, there are circulating procoagulants that shorten the PTT. � Extensive cancer (ovarian, pancreatic, colon), except when the liver is involved � An acute-phase reaction: this is a condition causing pronounced tissue inflammation or trauma that elevates factor VIII levels. It is usually a temporary change that is not monitored with a PTT test. When the condition causing the acute phase reaction is resolved, the PTT will return to normal
How to prepare for the Test:
The health care provider may tell you to stop taking certain drugs before the test. Drugs that can affect the results of a PTT test include antihistamines, vitamin C (ascorbic acid), aspirin, and chlorpromazine (Thorazine). Do not stop taking any medicine without first talking to your doctor.