This test measures the amount of troponin I in the blood. Troponin I is a protein found in the heart muscle fibers. It is used to help a healthcare professional diagnose a heart attack.
Who is a candidate for the test?
If the healthcare professional suspects a heart attack has occurred or is in the process of occurring, he or she may order this test.
How is the test performed?
In order to measure the amount of troponin I in the blood, a blood sample is taken from a vein on the forearm or hand. First, the skin over the vein is cleaned with an antiseptic. Next, a rubber tube called a tourniquet is tied around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them. A fine needle is gently inserted into a vein, and the tourniquet is removed. Blood flows from the vein through the needle and is collected in a syringe or vial for testing in the laboratory. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.
What is involved in preparation for the test?
Normally, no preparation is required for this test.
What do the test results mean?
If a heart attack has taken place, the amount of troponin I in the blood will start to rise within the first 4 to 6 hours. The healthcare professional may order serial blood tests to see if the levels rise, indicating heart damage. In some cases the first level may be elevated, indicating an impending or a recent heart attack. The levels of this test "peak" at 24 hours and may last in the blood stream for several days. The test can help diagnose a heart attack early to ensure rapid treatment.
Other conditions or illnesses can cause a rise in the troponin level. Examples are a pulmonary embolus (a blood clot in the lung), pericarditis, or myocarditis.
The normal value for troponin I is less than 0.5 ng/ml.