Let's learn about the PT/INR test. This is how your blood clotting rate is measured (Prothrombin Time / INR Test)

Have you ever had a minor injury? Maybe you cut your hand with a knife, or you fell somewhere. When that happens, the bleeding stops after a while, right? The reason for this is an amazing mechanism in our body. That is blood clotting. But sometimes this process does not work properly. Either the blood takes longer than it should, or it happens faster than it should. In such cases, we are talking about a very simple, but very important test that is done to find out exactly how fast your blood clots. It is called the Prothrombin Time, or PT/INR test.

Simply put, what is this PT/INR test?

The PT/INR test is a test that takes a sample of your blood and measures how long it takes for it to clot. Think about it, when you have an injury, proteins in our bodies (called clotting factors) work together to form a blood clot to stop bleeding. Prothrombin is another protein that is made by our liver and is essential for the blood clotting process.

The results of this test can be given in seconds, or they are often given in a special calculation called ``INR - International Normalized Ratio''. INR is a standard measurement that does not vary from lab to lab around the world. Therefore, it is very easy for doctors to understand the results.

Often, the doctor will also do another blood clotting test called PTT (Partial Thromboplastin Time) along with this PT test. It checks whether the other factors that help blood clot are working properly.

In what situations is this PT/INR test performed?

Doctors do this test to make sure your blood is clotting properly. Just think, if your blood is slow to clot, you can bleed excessively even from a small injury. Similarly, if your blood clots too quickly, the clots can get stuck in your blood vessels and cause dangerous conditions.

Here are some of the main reasons your doctor might perform this test:

• Monitor your warfarin dosage: Warfarin, also known as Coumadin®, is a blood thinner. It is given to prevent dangerous blood clots from forming inside the body. For example, this medication is given to people who are at risk for blood clots in the veins of the legs (Deep Venous Thrombosis) or blood clots in the lungs (Pulmonary Embolism). So, this PT/INR test is often done to see if the dose of warfarin you are taking is right, too much, or not enough.

• Before Surgery: This test is done before an operation to see if your blood clots normally. This will help the doctors make sure that there is no risk of excessive bleeding during the operation.

• Diagnose bleeding and blood clotting disorders: If you have unexplained bruising, frequent nosebleeds, or difficulty stopping bleeding from even a small wound, this test can help determine the cause.

• If you suspect liver disease: We mentioned earlier that prothrombin is made by the liver. So, if there is a problem with this protein, it could mean that there is a liver disease. The PT/INR test is one of several tests used to check liver function.

Is there any special preparation required before the test?

Yes, sometimes a little preparation may be needed. Your doctor will explain this to you. Typically, it may be something like this:

• Stop some medications temporarily: Some medications, such as antibiotics, can increase your PT/INR. Hormonal medications, such as birth control pills, can also decrease this value. Therefore, you should tell your doctor about all the medications you are taking. But remember, never stop your medications unless your doctor tells you to.

• Reduce your intake of Vitamin K: Vitamin K is a substance that helps blood clot. So if you take vitamin K pills, or eat a lot of vitamin K-rich foods like cabbage, spinach, and broccoli, you may be asked to reduce them a little. Because that can also affect the results. But before doing any of these, you should definitely ask your doctor.

What happens during the test?

This is very simple, just like donating blood normally.

1. A nurse or lab technician will swab the inside of your arm with alcohol and place an elastic band around the top of your arm.

2. Then they will ask you to rub your hand. Then you will see the veins clearly.

3. A needle is used to draw some blood from the vein into a small vial. You will feel a slight stinging sensation when the needle is inserted.

4. When the blood is drawn, you will be asked to place a small plaster or piece of cotton over the needle and hold it in place.

Sometimes, especially for people taking warfarin, they have to do the test regularly, so they have to take a drop of blood from their fingertip. There are also at-home test kits. If you want one, your doctor will show you how to use it and how to report the results to your doctor.

Results or how to understand the results?

When you get your results, let's see what the numbers mean. This is very important to understand, especially if you are taking warfarin.

What do abnormal results mean?

If the PT value or INR value is high:

This means that your blood takes longer than normal to clot.

• If you are not taking warfarin, this may be due to a bleeding disorder, liver problem, or vitamin K deficiency.
• If you are taking warfarin and your INR is higher than the target (e.g., greater than 3.0), you are at risk of bleeding. This may be due to:
• Your warfarin dose is a little too high.
• Because of another medication you took without telling the doctor (some painkillers, cold medicine).
• Warfarin interactions with things like spinach, kale, cranberry juice, or alcohol.

If the PT value or INR value is low:

This means that your blood clots more quickly than normal. If a person taking warfarin has an INR value below the target (e.g., less than 2.0), there is still a risk of blood clots forming.

If the results are abnormal, what do you do next?

Based on the results, your doctor will decide what to do next.

• If you are taking warfarin: Your doctor will adjust your dose slightly to bring your INR back into the target range. This means you may need to increase or decrease your dose slightly.
• If another disease is suspected: The doctor will consider the results of both the PT and PTT tests together. He or she may also refer you for further tests to diagnose the disease.

Results are usually available within a few hours or a day. A fingerstick test takes just a few minutes.

PT/INR test, blood clotting, prothrombin time, INR, warfarin, Coumadin, blood thinners, liver, vitamin K, bleeding disorders, blood clotting