The Protine INR [PT/INR] blood test is ordered by a doctor when a patient has bleeding that cannot be explained in some way. It is often ordered in conjunction with a PTT [partial thromboplastin time] test and evaluates the common and extrinsic pathways of coagulation. With the PTT results, a patient’s coagulation factors can be experienced.
The most common reason for this test to be ordered is to determine how effective a warfarin treatment is progressing. Warfarin, which is also commonly known as Coumadin, helps to thin out the blood so that clots do not form. Those with deep vein thrombosis, a pulmonary embolism, or artificial heart valves are on this medication often, which means they will receive the blood test often. Those with bleeding that does not stop or internal bleeding which can’t be sourced may also have the PT/INR blood test ordered.
Blood for the test can be obtained from a vein sample or through a fingerstick. No test preparation is generally necessary.
The PT/INR May Be Ordered Without Symptoms
Many patients worry about being ordered to have this blood test done. Many doctors will order the PT/INR without there being any symptoms just to make sure a treatment plan is progressing appropriately. It will determine if clotting time is at appropriate levels without causing bruising or bleeding that may be painful or even life threatening.
If warfarin isn’t being taken, then the PT/INR blood test is typically ordered to determine chronic bleeding. Someone with a bloody nose 5x per week, for example, may be asked to have this blood test taken. People with chronic anemia, suddenly poor eyesight, or blood in places where there isn’t supposed to be blood will also have this test ordered for diagnostic purposes.
What Do the Results of the PT/INR Mean?
For patients that have a confirmed bleeding or clotting syndrome, the PT/INR and PTT blood test results can mean several different things based on four different result combinations.
PT Prolonged/PTT Normal. This is an indication of liver disease. There may also be a deficiency in Vitamin K. This is a normal result for those who are taking warfarin.
PT Normal/PTT Prolonged. This may be an indication that there is a lupus anticoagulant present in the blood. There may also be von Willebrand disease present.
PT Prolonged/PTT Prolonged. This result is usually a result of severe liver disease. There may also be severe disseminated intravascular coagulation present.
PT Normal/PTT Normal. This means that there is likely a normal clotting presence, but mild deficiencies may still exist.
If this blood test has been ordered, then it is important to refrain from drinking alcohol as it can affect the outcome of the test. Certain antibiotics may also alter the results of the test to make them inaccurate. Certain foods contain a lot of Vitamin K and alter the results as well, so care should be taken in eating kale, beef, broccoli, and soybean products before the test. Make sure you speak to your medical provider about any supplements that you are taking and your dietary choices so that a correct PT/INR order may be issued.
Hormone replacement therapies, oral contraceptives, and barbituates may also negatively impact the PT/INR blood test. Speak with your doctor about temporarily halting your treatments for this test so an accurate result can be achieved.
The PT/INR Blood Test Can Be Taken At Home
For patients who are taking warfarin for an extended period of time, the FDA has approved a home testing system that can be used. It is issued in conjunction with a thorough patient training program that will have several management response protocols in place.
If you have the Protime INR blood test on a regular basis and the results are varying from time to time, there is not usually a reason to concern. Changes in diet from day to day can result in different test results. How the blood is collected or if it is difficult to obtain also impact the PT/INR results. If a doctor is not concerned about the results, then a second opinion can be requested or trust in the doctor’s opinion can be had.
It is not necessary to schedule the protime INR blood test on the same day that it is ordered. Patients who are taking warfarin should continue with their treatments to maintain therapeutic levels of the medication. Increases or decreases in the amount of warfarin being taken will often result in a PT/INR order.