Hey everyone, it's Sarah, the registered nurse, RN.com, and today we're going to talk about the PT-INR blood test. And as always, whenever you get done watching this YouTube video, you can access the free quiz that will test you over this content. So let's get started.
What is a PT-INR? This is a blood test that assesses how fast the blood clots. And how we collect this test is that we stick a patient's vein with a needle, we remove some blood, put it in a specific tube. and we send it to a lab who will run this test.
Now PT, it stands for prothrombin, and prothrombin is actually a clotting factor, specifically clotting factor two. So clotting factor two, along with the other clotting factors in this coagulation cascade, are activated in a certain sequence that leads to the formation of a clot. So prothrombin plays a huge role in that.
The INR stands for international normalized ratio. The INR is really important for patients who are taking warfarin, also called Coumadin, which is an anticoagulant because that medication, its whole goal is to help prolong how long it takes a patient to form a clot. We calculate the INR level based on this PT level.
They wanted to create a standardized way of reporting. supporting this PT level because when a patient's on warfarin you have to monitor them very closely and whatever this INR level is that dosage of warfarin will be adjusted. So a PT INR level is not only helpful in monitoring a patient who's taking warfarin but it's helpful in helping diagnose a potential bleeding disorder the patient may have because this PT INR level is going to look specifically at the extrinsic pathway of the coagulation cascade. And a lot of times it can be ordered alongside an APTT, which is an activated partial thromboplastin time.
And we're going to talk about that in the next video. Now let's talk a little bit more about prothrombin and the coagulation cascade, because this is going to help us truly understand what we're looking at in these patients whenever we're collecting these lab results. specifically the clotting factors that are involved. So prothrombin, as I pointed out earlier, is a clotting factor, specifically clotting factor 2. Now the word prothrombin, the prefix pro means before proceeding. So what prothrombin is going to do, it's going to turn into thrombin with the help of factor 5 in this whole coagulation cascade.
And whenever thrombin is on board, it's really going to get things going because it's going to help turn fibrinogen into fibrin. And fibrin, as we learned in our deep vein thrombosis review, is really that main ingredient that helps that clot form because it's a mesh-like substance that causes things to stick to it. So that clot will be nice and formed and help prevent excessive bleeding.
And prothrombin, along with other clotting factors, are really dependent on vitamin K, which is produced in the liver. And I want to point that out for two reasons. One, A lot of times if a patient's PT-INR level is out of range, it could indicate that they have some type of liver issues going on because their body's not making vitamin K like it should and they can't get these clotting factors on board to help with clot formation.
Also warfarin, that anticoagulant I was talking about earlier with the INR, what kind of medication was that? What do we call that? We call that a vitamin K antagonist. So it works against vitamin K because remember the whole goal of warfarin and Coumadin is to prolong how long it takes a clot to Form in the body. So that is where that comes from.
So I hope that helps you connect the dots with that Now let's talk about the coagulation cascade So whenever a patient becomes injured whether they're injured Externally where they're going to lose a lot of blood out of that vascular system or they're injured internally in that vascular system you're going to have this coagulation cascade activated because it's going to try to save the person's life because it doesn't want to deplete that vascular system of all the blood. Because if we lose all of our blood, we're dead. We have nothing to pump and perfuse our organs and body and we can't survive. So this system wants to save our life. And it's made up of three pathways.
We have the extrinsic pathway, intrinsic pathway, and the common pathway. And this is where these two pathways, intrinsic and extrinsic, meet together at the common pathway and it ends in clot formation. PT level, PTINR, is actually going to check the extrinsic pathway.
That's what we care about for this one. Intrinsic, that's where the APTT comes into play, and we'll talk about that in the next lecture. So just to quickly review, the extrinsic pathway, it is activated when we have external injury outside of the vascular system.
that's going to deplete it. The intrinsic is whenever you have injury inside the vascular system and it's activated but regardless of the cause what's going to happen they'll meet together at this common pathway and have a clot form. But what what's cool is depending on what pathway is activated will depend on what clotting factors are activated.
And there's about 13 clotting factors. So what you want to know is what clotting factors the PTI and R level is going to check. Well, it's going to check the ones that make up the extrinsic pathway.
So the extrinsic pathway, when it's activated, we have factor seven. So we're going to look at factor seven. Then it's going to check the common pathway, which is factor one, two, five, and 10. So with the the PT-INR, the clotting factors you're going to check will be factor 1, 2, 5, 10, and 7. So now let's wrap up this review and let's take what we have learned and apply it to what we need to know as the nurse. So in summary, the PT-INR level is a test that tells us really how well that extrinsic pathway and common pathway are working together. So in the end, it's going to tell us how fast prothrombin turns in.
thrombin which is going to help set that whole cascade and allowing a clot to form because we're gonna get fibrin on and that's gonna cause our clot so the PT level the prothrombin level is measured in seconds now the normal range varies because depending on the laboratory they use different testing agents but generally a normal PT level is about 10 to 12 seconds so let's say that it's higher than that what could be gone on with your patient? Well, your patient may have a clotting disorder. It's taking them a long time to form a clot.
They could have vitamin K deficiency because remember that liver produces vitamin K clotting factors. Many of them are dependent on vitamin K to work. So maybe they're low on that.
They could have some type of cancer, liver disease, or they may be on an anticoagulant, which leads us to the INR, the international normalized ratio. Again, that was calculated from the peach. PT level, it just gives us a standard way of reporting this PT level for patients who are on that warfarin slash coumadin.
So a normal INR level is generally less than 1.1. And if a patient's on warfarin, where do you want them at on their INR level? About 2 to 3. So test question.
If your patient's taking warfarin, but their INR is less than 2, what is your patient at risk for? Well, they're at risk for developing clots because they're not... therapeutic. How about if their INR level was greater than three?
They're at risk for excessive bleeding because their clotting levels are really prolonged. So you want to keep those concepts in mind. Okay, so that wraps up this review over the PT INR. And don't forget to take the free quiz that will test you over this content.