Pt/PTT INR Testing
Prothrombin time (PT) is a blood test that measures how long it takes blood to clot. A prothrombin time test can be used to check for bleeding problems. PT is also used to check whether medicine to prevent blood clots is working.
A PT test may also be called an INR test. INR (international normalized ratio) stands for a way of standardizing the results of prothrombin time tests, no matter the testing method. It lets your doctor understand results in the same way even when they come from different labs and different test methods. In some labs, only the INR is reported and the PT is not reported.
Other blood clotting tests, such as partial thromboplastin time (PTT) and activated clotting time (aPTT), might be used if you take another type of blood-thinning medicine called heparin. These tests measure other clotting factors, or they may be used to see if you are getting the right dose of heparin. Partial thromboplastin time and prothrombin time are often done at the same time to check for bleeding problems or the chance for too much bleeding in surgery.
Blood clotting factors are needed for blood to clot (coagulation). Prothrombin, or factor II, is one of the clotting factors made by the liver. Vitamin K is needed to make prothrombin and other clotting factors. Prothrombin time is an important test because it checks to see if five different blood clotting factors (factors I, II, V, VII, and X) are present. The prothrombin time is made longer by:
- Blood-thinning medicine, such as warfarin.
- Low levels of blood clotting factors.
- A change in the activity of any of the clotting factors.
- The absence of any of the clotting factors.
- Other substances, called inhibitors, that affect the clotting factors.
- An increase in the use of the clotting factors.
- An abnormal prothrombin time is often caused by liver disease or injury or by treatment with blood thinners.
Advanced lipid testing may be recommended by your healthcare provider to optimize your cholesterol treatment. Advanced lipid tests are performed because standard cholesterol tests may not completely represent cholesterol-related risk for heart attacks and strokes. Some people—especially people with diabetes, insulin resistance, or cardiovascular disease—continue to have progression of cardiovascular disease, even when their low-density lipoprotein (LDL) cholesterol is at goal.
Advanced lipid testing is usually performed in addition to a standard cholesterol test or “lipid panel,” which measures total
cholesterol, LDL cholesterol, high-density lipoprotein (HDL) cholesterol and triglycerides. Two commonly used advanced lipid tests are apolipoprotein B (apoB) and LDL particle number (LDL-P).
How are advanced lipid tests performed and how often should I have testing?
ApoB and LDL-P are both simple blood tests and do not require fasting. Advanced lipid testing is oered at many labs and also
may be available at your healthcare provider’s oce. Insurance coverage can be discussed with your healthcare provider and
insurance company. Some providers recommend advanced lipid testing at the initial visit and intermittently throughout
treatment. Some providers recommend advanced lipid testing after you have successfully achieved your LDL cholesterol and
non-HDL cholesterol goals.
What are good results and how do I achieve them?
As with standard cholesterol testing, your healthcare provider may recommend a specific target number based on your risk factors. As with cholesterol goals, advanced lipid goals are reached through a combination of healthy lifestyle and cholesterol-lowering medication.
How are advanced lipid tests different from regular cholesterol tests?
Cholesterol is carried in lipoprotein particles. Advanced lipid tests can be useful because some people do not have a lot of LDL cholesterol, but they have a lot of LDL particles. This can occur when they have mostly small particles or, alternatively, particles that contain less cholesterol per particle. A higher number of these lipoprotein particles make it easier for them to invade the walls of the arteries and induce a series of events that can lead to plaque formation.
The LDL particle number measures the actual number of LDL particles that carry LDL cholesterol per liter of plasma. In addition to the number of LDL particles, advanced lipid tests report the size of these LDL particles, which may help your provider diagnose the cause of your cholesterol abnormality.
For example, increased numbers of small, dense LDL particles can be caused by insulin resistance, a condition that raises your risk for developing diabetes. Understanding this information will help your healthcare provider utilize the right combination of diet and drug therapy to prevent onset or progression of disease. The apoB test measures the concentration of lipoprotein
particles that have an apolipoprotein B on their surface. All of the particles that have the potential to cause disease are
labeled with one molecule of apo B. ApoB, like LDL-P, can be a better measure of risk than LDL cholesterol in certain people.