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Prothrombin Time (PT) Test


The prothrombin time (PT) test uses blood samples to analyse how quickly your blood forms a clot. Healthcare providers often do this test to monitor prothrombin levels if you are taking any blood thinner like warfarin.


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What is the Prothrombin Time test? 

Prothrombin time (PT) is a test to estimate the ability of the plasma to clot. This test is used to evaluate bleeding disorders and also to check the efficiency of the ongoing anticoagulant medication. It is also advised before undergoing any surgical procedure. This test assesses the functioning of blood coagulation factors I, II, V, VII, and X, and the time taken for the conversion of prothrombin to thrombin.

The Prothrombin Time International Normalised Ratio PT (INR) has been calculated from PT results and PT (INR) if higher than normal indicates blood will take a longer time to clot, while values shorter than normal could indicate a clotting disorder where blood takes less time to clot.

What are the other names for the Prothrombin Time test? 

The other names are PT test, PT INR, and INR test.

What are the test parameters included in the Prothrombin Time test?

There is only one parameter: Prothrombin Time.

What does a Prothrombin Time test measure? 

The Prothrombin Time (PT) Test measures the ability of the plasma to clot in order to find a bleeding disorder or clotting disorder and to monitor the effects of the anticoagulant medication, Warfarin, heparin, aspirin, and acitrom.

In the event of any bleeding, the body responds by forming a blood clot as quickly as possible. This type of process in blood clotting or coagulation is called hemostasis and involves a series of chemical reactions in the blood (coagulation cascade) that activate blood proteins called coagulation factors one after another in a series. These activated coagulation factors lead to the formation of fibrin mesh around the platelets and other blood cells at the site of the bleeding, and this complex hardens to form a “blood clot."

The coagulation cascade proceeds through two pathways: the intrinsic pathway and the extrinsic pathway. These pathways, afterward, merge together into common pathways. Prothrombin (Coagulation Factor II) is converted to its active form, thrombin, in one of the reactions. Prothrombin test assesses the functioning of blood coagulation factors I, II, V, VII, and X, which are parts of the extrinsic and common pathways, by analyzing the time taken for conversion of prothrombin to thrombin. The Activated Partial Thromboplastin Time (aPTT) Test measures the functioning of blood coagulation factors I, II, V, XII, VIII, IX, X, and XI, along with other factors like Prekallikrein (PK), and the High Molecular Weight Kininogen (HK), that form parts of the intrinsic and common coagulation pathways. The PT and aPTT tests are usually processed together, and the results of both are evaluated simultaneously to determine the rate of blood clotting.

Warfarin is prescribed for the treatment of the conditions caused or worsened by excessive blood clotting like Deep Vein Thrombosis (DVT) (blood clot formation in blood vessels), irregular heartbeats, etc. The PT test is also done to evaluate the effectiveness of warfarin treatment. When it is performed to determine the Warfarin efficiency, the result of the PT test is expressed in terms of a measurement scale called the International Normalized Ratio (INR). Since the PT tests are processed using the different reagents in different labs, giving rise to widely varying results in other conventional units, the INR system was created to maintain uniformity in the results.

 

What’s the normal range of Prothrombin Time test? 

  • Prothrombin time (PT): 8.7-11.5 seconds.

  • International normalised ratio (INR): 0.8-1.2

  • INR During Warfarin Treatment: 2.0 to 3.0

Who should get a Prothrombin Time test? 

If the doctor suspects that you have a bleeding disorder, he may order a PT test to help them make a diagnosis. Even if you have no symptoms of a bleeding disorder, your doctor may order a PT test to make sure your blood is clotting normally before you may undergo major surgery.

When we get a cut and the blood vessel ruptures, the blood platelets collect at the site of the wound. They create a temporary plug to stop the bleeding. To produce a strong blood clot, a series of 12 plasma proteins, or the coagulation “factors,” act together to make a substance called fibrin that seals the wound.A bleeding disorder known as haemophilia could cause your body to create certain coagulation factors incorrectly, or not at all. Some medications, liver disease, or vitamin K deficiency may also cause abnormal clot formation.

Symptoms of a bleeding disorder include:

  • Easy bruising

  • The bleeding won’t stop even after applying pressure to the wound.

  • Heavy menstrual periods

  • blood in the urine

  • swollen or painful joints.

  • nosebleeds

In case you’re taking the blood-thinning medication warfarin, your doctor will order regular PT tests to ensure you’re not taking too much medication. Taking too much warfarin may cause excessive bleeding.

Are preparations needed for the Prothrombin Time test?

There is no preparation required for this test. Fasting is not required.

What is the cost of a Prothrombin Time test?

What is the type of sample required? 

This test requires a blood sample.

Who performs a Prothrombin Time test?

A healthcare provider, who is also called a phlebotomist, usually performs blood draws, including those for Prothrombin Time tests, but any healthcare provider trained in drawing blood can perform this task. The samples are sent to a lab where a medical laboratory scientist prepares the samples and performs the tests on analysers or manually.

What should I expect during my Prothrombin Time test?

You can expect to experience the following during the blood test or a blood draw:

  • You will have to sit comfortably on the chair, and a healthcare provider will check your arms for an easily accessible vein. It is the inner part of your arm on the other side of your elbow.

  • Once they have located a vein, they will clean and disinfect the area with an alcohol swab.

  • Then they will insert a small needle into your vein to draw a blood sample. This might feel like a small pinch.

  • After they insert the needle, the required amount of blood will be collected in a test tube.

  • When they have collected enough blood for the test, they’ll remove the needle and hold a cotton ball or gauze on the site to stop any bleeding.

  • They will put a band-aid over the pricked site, and the blood collection is finished.

This process takes less than five minutes.

What should I expect after my Prothrombin Time test?

Once the healthcare provider has collected the blood sample, it will be sent to the laboratory for processing or testing. When the test reports are ready, your healthcare provider will share the results with you.

What is the risk of the Prothrombin Time test?

These blood tests are very common and don’t carry any significant risks. You may have a  slight pain like an ant bite when the needle gets inserted, and a small bruise may develop there.

When can I expect my Prothrombin Time test results?

At Orange Health reports are available via email or WhatsApp within 6 hours of the collection of the blood sample.

 

What do the results of a Prothrombin Time test mean?

For those who are taking warfarin, most laboratories report PT results that have been adjusted to the INR. They must have an INR of 2.0 to 3.0 for basic “blood-thinning” needs. For those who may have a high risk of a blood clot, the INR needs to be higher – about 2.5 to 3.5.

For individuals who are not on warfarin, the reference range for a PT depends on the methodology used, with results measured in seconds and compared to the normal range established and maintained by the laboratory that processes the test. These normal ranges represent the average value of healthy people who live in that area and will vary from lab to lab. Someone who is not taking any warfarin would compare their PT test result to the normal range that is provided with the test result by the laboratory performing the test.

Prolonged PT means that the blood is taking too much time to form a clot. This may be caused by conditions such as liver disease, vitamin K deficiency, or coagulation factor deficiency (e.g., factor VII deficiency). PT report is often interpreted with  PTT in evaluating what conditions may be present.

What are normal Prothrombin Time test results?

  • Prothrombin time (PT): 8.7-11.5 seconds.

  • International normalised ratio (INR): 0.8-1.2

  • INR During Warfarin Treatment: 2.0 to 3.0

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different samples. Talk to your health care provider about the meaning of your specific test results.

What other tests might I have along with this test?

aPTT, Von Willebrand factor test, and Thrombin Time.

How do I book a Prothrombin Time test at home?

Log on to www.orangehealth.in and submit your details. Our highly trained and vaccinated eMedics will be at your doorstep within 60 minutes or at the slot booked by you.

Frequently Asked Questions on Prothrombin Time test

What happens if prothrombin time is high?

A high prothrombin time (PT) on a blood test is a sign of a coagulation disorder. It means that it takes a long time for the blood to form a clot to stop haemorrhage and therefore there is excessive bleeding. A high prothrombin time (PT) in a blood test can be a sign of liver disease, vitamin K deficiency, and disseminated intravascular coagulation (DIC) by excessive coagulation factors consumption. 

 

Why is the prothrombin time test done?

A prothrombin time (PT) test uses blood samples to analyse how quickly your blood forms a clot. Your doctor often does this test to monitor your prothrombin values if you are taking the blood thinner warfarin. Usually, this test is also used to investigate potential blood disorders. 

 

What does an INR of 1.0 mean?

In healthy people, an INR of 1.0 is considered normal. An INR range of 2.0 to 3.0 is generally an effective therapeutic range for people who are taking warfarin for disorders. 

 

What if prothrombin time is low?

A low prothrombin time (PT) in a blood test is considered normal and has no clinical meaning. This is not used for the diagnosis of disease. If the prothrombin time is low, it means that when there is a haemorrhage, the clots are formed very quickly and the bleeding stops quickly.

 

What is the critical INR level?

An INR value of above 4.5 is considered a critical level and increases the risk of fatalities through bleeding.


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