The PT INR [prothrombin time] blood test is ordered when someone is experiencing bleeding from an unexpected source. It is often ordered with the PTT blood test to examine an individual’s coagulation factors as it examines all of the pathways of the coagulation cascade. Sometimes it is used to determine if there is hidden bleeding before a surgery takes place, but it is most often ordered by medical providers to determine the effectiveness of a warfarin therapy.
Warfarin, which is also known by its brand name of Coumadin, is used to stop the formation of blood clots. It may be ordered on a short-term basis to limit the risks of a negative cardiac event or stroke or on a long-term basis when someone is suffering from blood clotting issues. Pulmonary embolisms, deep vein thrombosis, or as a co-treatment factor for the placement of an artificial heart valve are the most common reasons why warfarin will be prescribed.
The goal is simple: to balance out the risks of excessive bleeding with the risks of inappropriate clotting. The PT INR blood test helps to measure this balance to determine if treatment plan adjustments may be necessary.
When Is the PT INR Blood Test Ordered?
A medical provider will order ongoing PT INR blood tests to make sure that anticoagulant medications are working as they should. The frequency of these blood tests is individualized and is ordered so that there is confirmation that its desired effect is being obtained. It may also be ordered if there are the symptoms of a bleeding disorder, such as frequent nosebleeds or blood in bowel movements, chronic anemia, or changes to vision.
Some medical providers will also order the test to ensure that a patient has a normal clotting function prior to a surgery.
What Do My Test Results Mean?
A normal test result on the PT INR blood test is generally between 2-3 and this is because the test results are generally adjusted automatically because it is ordered to monitor warfarin therapy so often. For individuals who have a high risk of forming inappropriate clots, a normal test result will be 2.5-3.5 instead. The normal test results can also be adjusted by a medical provider based on an individual’s medical history.
These test results are often compared to the PTT blood test results to measure how long it takes for a blood clot to form. This means that the results will either be considered normal or “prolonged,” which means it takes longer for the PT INR or PTT blood test to form a clot when compared to the other. Based on these results, certain health conditions may be present.
1. The PT INR blood test shows prolonged results, but the PTT result is normal.
This indications a Vitamin K deficiency, the presence of warfarin, or the possibility of liver disease.
2. The PT INR blood test is normal, but the PTT result is prolonged.
In some individuals, this may indicate the presence of lupus. Other defective factors may also be present, as can certain genetic diseases.
3. The PT INR and PTT results are both considered prolonged.
This can indicate severe liver disease, an acute genetic disorder, or other individualized health problems.
If both tests are considered normal, then this may still indicate that there are mild deficiencies in place that do not meet the qualification of an abnormal result. That’s why only a medical provider is qualified to determine what individualized results mean for each test.
Here’s What You Need To Know
Alcohol consumption can directly affect the results of the PT INR blood test. Some individuals may be asked to abstain from alcoholic beverages or alcohol-containing medications, like cough medicine, for a certain period of time before the test to make sure the results are valid.
Certain antibiotics may also cause inaccurate test results, as can certain oral contraceptives, hormone replacement therapies, and excessive Vitamin K consumption. Depending on the reason why these medications are being taken, there may be a delay before the blood test is ordered so that the medication regimen can run its course.
Some individuals may be allowed to take this blood test at home, especially if the warfarin therapy is given on an extended basis. A home care provider may be required to administer the test, however, so scheduling may still be necessary. The test can be done at just about any time of day and certain variations in the results are expected, especially for those who consume large numbers of soybean products, green tea, and certain other foods.
The PT INR blood test results explained here can help someone know what their blood balance happens to be. By maintaining it appropriately, a treatment plan can continue to provide needed benefits.