Description: A Prothrombin with INR and Partial Thromboplastin Times test is used to diagnose and monitor bleeding disorders or excessive clotting disorders. The biomarkers in the test are used to measure the time it takes for the blood to form a clot.
Also Known As: Pro Time with INR Test, Prothrombin Time and International Normalized Ratio test, Prothrombin Time PT with INR Test, Prothrombin Time with INR Test, Prothrombin with INR, Protime with INR, PT Test, Activated Partial Thromboplastin Time Test, aPTT test, PTT Test
Collection Method: Blood Draw
Specimen Type: Whole Blood
Test Preparation: No preparation required
Average Processing Time: 1 to 2 days
When is a Prothrombin with INR and Partial Thromboplastin Time test ordered?
When a person takes the anticoagulant medicine warfarin, a PT and INR are ordered on a regular basis to confirm that the prescription is working effectively and that the PT/INR is adequately extended. A doctor will prescribe them frequently enough to ensure that the treatment is having the desired effect, namely, boosting the person's clotting time to a therapeutic level while minimizing the danger of excessive bleeding or bruising.
When a person who isn't taking anticoagulants exhibits signs or symptoms of excessive bleeding or clotting, a PT may be ordered when they are experiencing:
- Bleeding that isn't explained or bruises that isn't easy to get rid of
- Gums that are bleeding
- A blood clot in a vein or artery
- Disseminated intravascular coagulation
- A persistent disorder that affects hemostasis, such as severe liver disease
When a person has the following symptoms, the PTT may be ordered along with other tests, such as a PT:
- Bleeding that isn't explained or bruises that isn't easy to get rid of
- A blood clot in a vein or artery is a serious condition.
- Disseminated intravascular coagulation
- A chronic disorder that affects hemostasis, such as liver disease
A PTT can be requested in the following situations:
- When a person develops a blood clot or a woman has repeated miscarriages, as part of a lupus anticoagulant, anticardiolipin antibodies, or antiphospholipid syndrome examination
- When a person is on standard heparin therapy, the two are overlapped and both the PTT and PT are monitored until the person has stabilized. When a person is switched from heparin therapy to extended warfarin therapy, the two are combined and both the PTT and PT are monitored until the person has stabilized
- Prior to surgery, if there is a high risk of blood loss and/or if the patient has a history of bleeding, such as frequent or severe nasal bleeds and easy bruising, which could suggest the presence of a bleeding problem
What does a Prothrombin with INR and Partial Thromboplastin Time blood test check for?
The prothrombin time with INR and partial thromboplastin time is a test that determines a person's capacity to make blood clots properly. The international normalized ratio, or INR, is a calculation based on the results of a PT that is used to track people who are taking the blood thinner warfarin. The PTT evaluates the number and function of specific proteins known as coagulation factors, which are crucial in blood clot formation.
After chemicals are added to a person's blood sample, a PT measures how long it takes for a clot to develop. The PT is frequently used with a partial thromboplastin time to measure the number and function of proteins known as coagulation factors, which are essential for optimal blood clot formation.
When an injury develops in the body and bleeding ensues, the clotting process known as hemostasis begins. This process is aided by a series of chemical events known as the coagulation cascade, in which coagulation or "clotting" components are activated one by one, leading to the development of a clot. In order for normal clotting to occur, each coagulation factor must be present in appropriate quantities and operate effectively. Excessive bleeding can result from too little, while excessive clotting can result from too much.
There are two "pathways" that can trigger clotting in a test tube during a laboratory test, the extrinsic and intrinsic pathways. Both of these pathways subsequently converge to finish the clotting process. The PT test assesses how well all coagulation factors in the extrinsic and common routes of the coagulation cascade cooperate. Factors I, II, V, VII, and X are included. The PTT test examines the protein factors XII, XI, IX, VIII, X, V, II, and I, as well as prekallikrein and high molecular weight kininogen, which are all part of the intrinsic and common pathways. The PT and PTT examine the overall ability to generate a clot in a fair period of time, and the test results will be delayed if any of these elements are insufficient in quantity or are not operating effectively.
The PT test is normally done in seconds and the results are compared to a normal range that represents PT levels in healthy people. The normal ranges will fluctuate because the reagents used to perform the PT test differ from one laboratory to the next and even within the same laboratory over time. For people taking the anticoagulant warfarin, a World Health Organization committee developed and recommended the use of the Internationalized Normalized Ratio, which is calculated based on the PT test result, to standardize results across different laboratories in the United States and around the world.
The INR is a formula that accounts for variations in PT reagents and enables for comparison of findings from different laboratories. When a PT test is performed, most laboratories report both PT and INR readings. However, the INR should only be used by people who are taking the blood thinner warfarin.
Lab tests often ordered with a Prothrombin with INR and Partial Thromboplastin Time test:
- Fibrinogen Activity
- Platelet Count
- Complete Blood Count (CBC)
- Lupus Anticoagulant
- Von Willebrand Factor
- Antiphospholipid Antibodies
- Warfarin Sensitivity Testing
Conditions where a Prothrombin with INR and Partial Thromboplastin Time test is recommended:
- Bleeding Disorders
- Excessive Clotting Disorders
- Vitamin K Deficiency
- Liver Disease
- Antiphospholipid Syndrome
How does my health care provider use a Prothrombin with INR and Partial Thromboplastin Time test?
The prothrombin time is used to diagnose the origin of unexplained bleeding or abnormal blood clots, generally in conjunction with a partial thromboplastin time. The international normalized ratio is a calculation based on the results of a PT that is used to monitor people on the blood thinner warfarin.
Coagulation factors are proteins that are involved in the body's process of forming blood clots to assist stop bleeding. When an injury occurs and bleeding begins, coagulation factors are triggered in a series of events that finally assist in the formation of a clot. In order for normal clotting to occur, each coagulation factor must be present in appropriate quantities and operate effectively. Excessive bleeding can result from too little, while excessive clotting can result from too much.
The PT and INR are used to monitor the anticoagulant warfarin's efficacy. This medication influences the coagulation cascade's function and aids in the prevention of blood clots. It is given to those who have a history of recurrent abnormal blood clotting on a long-term basis. Warfarin therapy's purpose is to strike a balance between preventing blood clots and causing excessive bleeding. This equilibrium must be carefully monitored. The INR can be used to change a person's medication dosage in order to get their PT into the ideal range for them and their condition.
The PTT is mostly used to look into unexplained bleeding or clotting. It may be ordered in conjunction with a prothrombin time test to assess hemostasis, the body's process of forming blood clots to stop bleeding. Excessive bleeding or clotting issues are frequently investigated with these tests as a starting point.
Coagulation factors are proteins that have a role in hemostasis and the development of blood clots. When an injury occurs and bleeding begins, coagulation factors are triggered in a series of events that finally assist in the formation of a clot.
Prekallikrein and high molecular weight kininogen, as well as coagulation factors XII, XI, IX, VIII, X, V, II, and I, are all assessed using the PTT. The coagulation factors VII, X, V, II, and I are evaluated in a PT test. A health practitioner can determine what type of bleeding or clotting condition is present by combining the findings of the two tests. The PTT and PT aren't diagnostic, but they can help you figure out if you need more tests.
The following are some examples of PTT applications:
- To detect coagulation factor deficit; if the PTT is extended, additional tests can be performed to ascertain whether coagulation factors are deficient or malfunctioning, or to see if the blood contains an antibody to a coagulation factor.
- Nonspecific autoantibodies, such as lupus anticoagulant, can be detected and are linked to clotting episodes and recurrent miscarriages. As a result, PTT testing may be included in a clotting disorder panel to aid in the investigation of recurrent miscarriages or the diagnosis of antiphospholipid syndrome. The LA-sensitive PTT, a version of the PTT, could be used for this.
- Heparin is an anticoagulant medicine that is given intravenously or by injection to prevent and treat blood clots; it is used to monitor routine heparin anticoagulant therapy. PTT is extended as a result of it. Heparin must be constantly managed when it is used for medicinal purposes. If too much is given, the patient may bleed excessively; if not enough is given, the patient may continue to clot.
The PTT and PT tests are sometimes used to screen for potential bleeding tendencies before surgical or other invasive treatments based on carefully acquired patient histories.
Other tests that may be done in conjunction with a PTT or in response to aberrant results include:
- Platelet count — should be checked often during heparin therapy to detect any thrombocytopenia caused by the drug.
- Thrombin time testing – used to rule out the possibility of heparin contamination.
- Fibrinogen testing - to rule out a low level of fibrinogen as the cause of a delayed PTT.
- A second PTT test is conducted after a first PTT is delayed by mixing the person's plasma with pooled normal plasma. If the PTT time returns to normal, it indicates that one or more coagulation factors in the person's plasma are deficient. If the condition persists, it could be caused by the presence of an aberrant specific factor inhibitor or nonspecific lupus anticoagulant.
- Coagulation factor tests are used to determine how active coagulation factors are. They can identify low protein levels or proteins that aren't working properly. A coagulation factor's antigen level is occasionally tested.
- If the presence of lupus anticoagulant is suspected, a test for dilute Russell viper venom may be performed.
- Von Willebrand factor is a test that is sometimes conducted to see if von Willebrand disease is causing a prolonged PTT.
What do my PT with INR and PTT test results mean?
Most laboratories report PT findings that have been corrected to the INR for persons taking warfarin. For basic "blood-thinning" needs, these persons should have an INR of 2.0 to 3.0. Some people with a high risk of blood clot require a higher INR, about 2.5 to 3.5.
The outcome of a PT test is determined by the method utilized, with results measured in seconds and compared to a normal range defined and maintained by the laboratory that administers the test. This normal range is based on the average value of healthy persons in the area, and it will differ somewhat from test to lab. Someone who isn't on warfarin would compare their PT test result to the usual range provided by the laboratory that conducted the test.
A prolonged PT indicates that the blood is taking an excessive amount of time to clot. This can be caused by liver illness, vitamin K inadequacy, or a coagulation factor shortage, among other things. The PT result is frequently combined with the PTT result to determine what condition is present.
PTT findings are usually available in seconds. A normal clotting function is usually indicated by a PTT result that falls within a laboratory's reference interval. However, a single coagulation factor deficiency may be present in low to moderate amounts. The PTT should not be extended until the factor levels have dropped to 30% to 40% of normal. Lupus anticoagulant may also be present, but it is unlikely to affect the PTT result. A more sensitive LA-sensitive PTT or a dilute Russell viper venom time can be used to test for the lupus anticoagulant if it is suspected.
A delayed PTT indicates that clotting is taking longer than usual and could be caused by a number of factors. This frequently indicates that the body's clotting ability is being harmed by a coagulation factor deficit or a particular or nonspecific antibody. Defects in coagulation factors can be acquired or inherited.
It's possible that prolonged PTT tests are caused by:
- Von Willebrand disease is the most prevalent inherited bleeding disorder, and it inhibits platelet function because von Willebrand factor levels are low.
- Hemophilia A and B are two more inherited bleeding disorders that are caused by a lack of factors VIII and IX, respectively.
- Other coagulation factors, such as factors XII and XI, are deficient.
Deficiencies in acquired factors:
- A vitamin K insufficiency. Vitamin K is required for the production of clotting factors. Vitamin K deficiency is uncommon, but it can occur as a result of a poor diet, malabsorption issues, or the use of certain antibiotics over an extended period of time, for example.
- Because the liver produces the majority of coagulation components, liver illness might result in extended PT and PTT. PT is more likely to be prolonged than PTT in patients with liver disease and vitamin K insufficiency.
- A nonspecific inhibitor, such as lupus anticoagulant—the presence of these inhibitors is usually linked to abnormal clotting, but they can also lengthen the PTT. For further information, see the individual test articles.
- Antibodies that selectively target certain coagulation factors, such as antibodies that target factor VIII, are known as specific inhibitors. They can form in people who are receiving factor replacements or they can develop spontaneously as an autoantibody in people who have a bleeding condition. Factor-specific inhibitors have the potential to induce serious bleeding.
- Heparin is an anticoagulant that will prolong a PTT if it is present in the sample as a contaminant or as part of anticoagulation therapy. The goal PTT for anticoagulant therapy is usually 1.5 to 2.5 times longer than the pretreatment level.
- The PTT is not used to monitor warfarin anticoagulation therapy, but it may be influenced by it. The PT is commonly used to track warfarin therapy.
- Anticoagulation therapy with a direct thrombin inhibitor or a direct factor Xa inhibitor are examples of other anticoagulants.
- Leukemia, severe bleeding in pregnant women prior to or after delivery, and recurrent miscarriages can all cause elevated PTT levels
The PTT results are frequently combined with the PT results to determine what ailment is present.
PTT testing may be shortened as a result of:
- Disseminated intravascular coagulation—circulating procoagulants shorten the PTT in the early phases of DIC.
- Extensive cancer
- An acute-phase reaction is a disease that causes significant tissue inflammation or trauma, which causes factor VIII levels to rise. It's frequently a one-time occurrence that isn't tracked with a PTT test. The PTT will return to normal once the condition that caused the acute phase reaction is resolved.
We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.