Prothrombin Time Test and INR (PT/INR)

Prothrombin Time Test and INR (PT/INR)

10 to 13 seconds

INR (international normalized ratio)

1.1 or below

The therapeutic range for most patients on VKAs(Vit K antagonists ) is an INR of 2.0 to 3.0.

Results
Prothrombin time test results can be presented in two ways.

In seconds
The average time range for blood to clot is about 10 to 13 seconds. A number higher than that range means it takes blood longer than usual to clot. A number lower than that range means blood clots more quickly than normal.

The normal range for PT is 10 to 13 seconds. The normal INR for a healthy individual is 1.1 or below, and the therapeutic range for most patients on VKAs( Vit K antagonists) is an INR of 2.0 to 3.0.

An increased PT/INR for patients on VKAs
(vitamin K-antagonists ) may suggest a super-therapeutic level and will require medication dose adjustments to prevent bleeding.

In healthy people, an INR of 1.1 or below is considered normal. An INR range of 2.0 to 3.0 is generally an effective therapeutic range for people taking warfarin for certain disorders. These disorders include atrial fibrillation or a blood clot in the leg or lung. In certain situations, such as having a mechanical heart valve, you might need a slightly higher INR.

When the INR is higher than the recommended range, it means that your blood clots more slowly than desired. A lower INR means your blood clots more quickly than desired.

A prothrombin time (PT) test measures how long it takes for a clot to form in a blood sample. An INR (international normalized ratio) is a type of calculation based on PT test results.

Prothrombin is a protein made by the liver. It is one of several substances known as clotting (coagulation) factors. When you get a cut or other injury that causes bleeding, your clotting factors work together to form a blood clot. How fast your blood clots depends on the amount of clotting factors in your blood and whether they're working correctly. If your blood clots too slowly, you may bleed too much after an injury. If your blood clots too fast, dangerous clots may form in your arteries or veins.

A PT/INR test helps diagnose the cause of bleeding or clotting disorders. It also checks to see if a medicine that prevents blood clots is working the way it should.

What is it used for?
A PT/INR test is most often used to:

See how well warfarin is working. Warfarin is a blood-thinning medicine that's used to treat and prevent dangerous blood clots. (Coumadin is a common brand name for warfarin.)
Find out the reason for abnormal blood clots
Find out the reason for unusual bleeding
Check clotting function before surgery
Check for liver problems.

A PT/INR test is often done along with a partial thromboplastin time (PTT) test. A PTT test also checks for clotting problems.

Why do I need a PT/INR test?
You may need this test if you are taking warfarin on a regular basis. The test helps make sure you are taking the right dose.

If you are not taking warfarin, you may need this test if you have symptoms of a bleeding or clotting disorder.

Symptoms of a bleeding disorder include:

Unexplained heavy bleeding
Bruising easily
Unusually heavy nose bleeds
Unusually heavy menstrual periods in women
Symptoms of a clotting disorder include:

Leg pain or tenderness
Leg swelling
Redness or red streaks on the legs
Trouble breathing
Cough
Chest pain
Rapid heartbeat
In addition, you may need a PT/INR test if you are scheduled for surgery. It helps make sure your blood is clotting normally, so you won't lose too much blood during the procedure.

What do the results mean?
If you were tested because you are taking warfarin, your results will probably be in the form of INR levels. INR levels are often used because they make it easier to compare results from different labs and different test methods. If you are not taking warfarin, your results may be in the form of INR levels or the number of seconds it takes for your blood sample to clot (prothrombin time).

If you are taking warfarin:

INR levels that are too low may mean you are at risk for dangerous blood clots.
INR levels that are too high may mean you are at risk for dangerous bleeding.
Your healthcare provider will probably change your dose of warfarin to reduce these risks.

If you are not taking warfarin and your INR or prothrombin time results are not normal, it may mean one of the following conditions:

A bleeding disorder, is a condition in which the body can't clot blood properly, causing excessive bleeding
A clotting disorder, is a condition in which the body forms excessive clots in arteries or veins
Liver disease
Vitamin K deficiency. Vitamin K plays an important role in blood clotting


Clotting too slowly
Blood that clots too slowly can be caused by:

Blood-thinning medicines
Liver problems
Inadequate levels of proteins that cause blood to clot
Vitamin K deficiency
Other substances in your blood that prevent the work of clotting factors
Clotting too fast
Blood that clots too quickly can be caused by:

Supplements that contain vitamin K
High intake of foods that contain vitamin K, such as liver, broccoli, chickpeas, green tea, kale, turnip greens and products that contain soybeans
Estrogen-containing medications, such as birth control pills and hormone replacement therapy

 Warfarin: 
*W isconsin 
University
A lumni students made a R esearch 
*F oundation  and discovered a molecule that caused bleeding... warfarin.

Prothrombin time
 10 to 13 seconds.

Inputs courtesy: Veteran ENT Doctor with 41 years of experience.