Prothrombin with INR and Partial Thromboplastin Times

The Prothrombin with INR and Partial Thromboplastin Times test contains 1 test with 3 biomarkers.

Brief Description: The Prothrombin with International Normalized Ratio (INR) and Partial Thromboplastin Times (PTT) test is a blood test that evaluates the clotting function of the blood. It is ordered to assess the activity of specific proteins involved in the clotting process. This test helps healthcare providers diagnose and monitor bleeding or clotting disorders and determine the appropriate treatment.

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

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
  • Nosebleeds
  • 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:

When PT/INR and PTT are ordered, they're typically part of a broader evaluation of hemostasis (blood clotting) and related health issues. Here are some tests commonly ordered alongside them:

  1. Complete Blood Count (CBC) with Platelet Count:

    • Purpose: To evaluate overall blood health, including the number and quality of red blood cells, white blood cells, and platelets.
    • Why Is It Ordered: To identify conditions like anemia, thrombocytopenia (low platelet count), or thrombocytosis (high platelet count), which can affect bleeding and clotting.
  2. Fibrinogen:

    • Purpose: To measure the level of fibrinogen, a protein essential for blood clot formation.
    • Why Is It Ordered: To assess the final step of the clotting process. Abnormal fibrinogen levels can impact clotting and are part of the complete assessment of coagulation function.
  3. Liver Function Test:

    • Purpose: To assess the health of the liver.
    • Why Is It Ordered: Since many clotting factors are produced in the liver, liver dysfunction can significantly impact coagulation tests like PT/INR and PTT.
  4. D-Dimer:

    • Purpose: To detect fragments of breakdown products of a blood clot.
    • Why Is It Ordered: To assess for recent or ongoing clot formation and breakdown, which can be useful in diagnosing conditions like deep vein thrombosis (DVT) or disseminated intravascular coagulation (DIC).
  5. Vitamin K Level:

    • Purpose: To measure the level of vitamin K.
    • Why Is It Ordered: Vitamin K is essential for the synthesis of certain clotting factors. Deficiency can affect PT/INR.
  6. Antiphospholipid Antibodies:

    • Purpose: To test for antibodies associated with antiphospholipid syndrome, a disorder that increases the risk of clot formation.
    • Why Is It Ordered: To evaluate for an autoimmune cause of clotting abnormalities.
  7. Factor Assays (such as Factor VIII, IX, and XI):

    • Purpose: To measure the activity of specific clotting factors.
    • Why Is It Ordered: To identify deficiencies or abnormalities in specific clotting factors, especially when investigating causes of abnormal PTT.

These tests, when ordered alongside PT/INR and PTT, provide a comprehensive view of an individual’s clotting ability and potential bleeding disorders. They are crucial for diagnosing and managing conditions that affect blood clotting, monitoring anticoagulant therapy, and evaluating liver function. The specific combination of tests will depend on the individual’s symptoms, medical history, and the results of initial screenings.

Conditions where a Prothrombin with INR and Partial Thromboplastin Time test is recommended:

The Prothrombin with INR and PTT test is commonly ordered for conditions such as:

  1. Bleeding Disorders: Hemophilia, von Willebrand disease, and other clotting factor deficiencies may necessitate this test.

  2. Thrombophilia: Conditions predisposing to excessive clotting, like deep vein thrombosis (DVT) or pulmonary embolism (PE), may require monitoring.

  3. Liver Disease: Liver dysfunction can impact the production of clotting factors, leading to abnormal PT and PTT results.

  4. Anticoagulant Therapy: Patients on medications like warfarin or heparin need regular monitoring to maintain the appropriate level of anticoagulation.

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.

Most Common Questions About the Prothrombin with INR and Partial Thromboplastin Times test:

Understanding the Prothrombin Time with INR and Partial Thromboplastin Time Tests

What is the Prothrombin Time (PT) with INR and Partial Thromboplastin Time (PTT) test?

The PT with INR and PTT tests are blood tests that measure how long it takes for your blood to clot. PT and INR focus on the extrinsic and common pathways of coagulation, while PTT evaluates the intrinsic and common pathways.

Why is the PT with INR and PTT test important?

The PT with INR and PTT test helps assess the body's ability to form blood clots and helps determine if you're taking the correct dosage of blood-thinning medications, like warfarin. It also aids in diagnosing bleeding disorders.

When is a PT with INR and PTT test recommended?

A PT with INR and PTT test is often recommended when you're taking anticoagulant therapy, like warfarin, to ensure you're on the correct dosage. It may also be ordered if you have unexplained bleeding or bruising, or before you undergo a surgical procedure.

Interpreting PT with INR and PTT Test Results

What does a high PT with INR result mean?

A high PT with INR result could mean that your blood is taking too long to clot, which could be due to a vitamin K deficiency, liver disease, or anticoagulant therapy.

What does a low PT with INR result mean?

A low PT with INR result could mean that your blood is clotting too quickly, which could be due to conditions such as Factor V Leiden.

What does a high PTT result mean?

A high PTT result could suggest that your blood is taking too long to clot. This might be due to hemophilia, von Willebrand disease, or anticoagulant therapy.

What does a low PTT result mean?

A low PTT result is not typically a concern unless you have a history of thrombosis or blood clots.

PT with INR and PTT Test in Specific Conditions

How is the PT with INR and PTT test used in anticoagulant therapy?

The PT with INR test is commonly used to monitor patients on warfarin therapy. The goal is to maintain a balance where the blood is thin enough to prevent clotting but not so thin as to cause bleeding.

How are PT with INR and PTT tests used in the diagnosis of hemophilia?

A prolonged PTT test result may indicate a deficiency in one of the blood clotting factors, suggesting a possible diagnosis of hemophilia. Additional tests would be required to confirm this diagnosis.

How are PT with INR and PTT tests used in the diagnosis of liver disease?

The liver plays a crucial role in the production of clotting factors. Thus, a prolonged PT or PTT may indicate liver disease.

General Questions About the PT with INR and PTT Test

Can certain medications affect the PT with INR and PTT test results?

Yes, medications like warfarin, heparin, and certain antibiotics can affect PT with INR and PTT test results. You should inform your healthcare provider of all the medications you're taking.

Can PT with INR and PTT test results vary during the day?

PT and PTT levels can slightly fluctuate throughout the day. However, these variations are typically within the normal range and are not clinically significant.

Can PT with INR and PTT tests be used to assess the risk of excessive bleeding during surgery?

Yes, these tests can help assess the risk of excessive bleeding during and after surgery by providing information about how quickly your blood can clot.

What does the INR value in the PT with INR test represent?

INR, or International Normalized Ratio, is a standardized value that helps to eliminate variability in PT results from different labs. It's particularly important in monitoring the effectiveness of anticoagulant therapy.

Can the PT with INR and PTT test be used to diagnose vitamin K deficiency?

A prolonged PT with INR can indicate a deficiency in vitamin K, as this vitamin is essential for the synthesis of certain clotting factors.

Can PT with INR and PTT tests be used to assess the risk of stroke or heart attack?

While these tests provide information about the clotting ability of the blood, they do not directly assess the risk of stroke or heart attack. However, they are crucial in monitoring therapy meant to prevent these conditions, such as anticoagulant therapy.

How do lifestyle factors, like diet and alcohol consumption, affect PT with INR and PTT results?

Diet can influence these test results, particularly if you consume foods rich in vitamin K, which is involved in clotting. Alcohol can affect the liver's function, and since the liver produces clotting factors, heavy alcohol use can also affect these results.

How do conditions like lupus affect PT with INR and PTT results?

Lupus, an autoimmune disease, can sometimes cause the production of certain antibodies that interfere with clotting, potentially leading to prolonged PT and PTT results.

Can the PT with INR and PTT tests be used to diagnose deep vein thrombosis (DVT)?

While a normal PT and PTT do not rule out DVT, these tests can be used to monitor anticoagulant therapy in patients diagnosed with DVT.

How does pregnancy affect PT with INR and PTT test results?

During pregnancy, the body undergoes changes that make the blood more prone to clotting. This could potentially affect PT with INR and PTT results.

Can the PT with INR and PTT tests be used to diagnose disseminated intravascular coagulation (DIC)?

Yes, DIC, a serious condition in which the proteins that control blood clotting become abnormally active, can be indicated by a prolonged PT and PTT.

How does dehydration affect PT with INR and PTT results?

Dehydration can make the blood more viscous, potentially affecting coagulation and thus PT with INR and PTT results.

Can the PT with INR and PTT tests be used in the diagnosis of von Willebrand disease?

A prolonged PTT can be a sign of von Willebrand disease, a common inherited bleeding disorder. However, additional tests would be required for a definitive diagnosis.

Can the PT with INR and PTT tests be used to diagnose Factor V Leiden?

While PT with INR and PTT tests provide information about the coagulation process, a specific genetic test is needed to diagnose Factor V Leiden, a mutation that increases the risk of developing abnormal blood clots.

What other tests might be ordered with the PT with INR and PTT tests?

Other tests might include a complete blood count (CBC), fibrinogen level, liver function tests, and specific clotting factor tests, depending on the patient's medical history and presenting symptoms.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.

The following is a list of what is included in the item above. Click the test(s) below to view what biomarkers are measured along with an explanation of what the biomarker is measuring.

Also known as: APTT, PT, PT and PTT, PT/PTT, PTT

Inr

International normalized ratio (INR) - To check how well the blood-thinning medication (anticoagulant) warfarin (COUMADIN®) is working to prevent blood clots; to help detect and diagnose a bleeding disorder. Internationalized Normalized Ratio (INR) with the PT test for people who are receiving the anticoagulant warfarin (COUMADIN®).

Partial Thromboplastin

Pt

Prothrombin time (PT) is a blood test that measures the time it takes for the liquid portion (plasma) of your blood to clot.
*Process times are an estimate and are not guaranteed. The lab may need additional time due to weather, holidays, confirmation/repeat testing, or equipment maintenance.

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