Troponin Test

Troponin tests are mainly used in Accident and Emergency departments on people who have chest pain to see if they have had a heart attack or other damage to their heart. In a heart attack, a blood clot stops the normal flow of blood to the muscle and prevents the heart from receiving oxygen. Without oxygen the heart muscle cells to die and release their contents which include troponin, myoglobin, CK (creatine kinase) and CK-MB. Either a troponin I or troponin T test will be used by the laboratory. Troponins are occasionally used with other markers of heart damage, such as CK–MB. However, troponins are the preferred test for a suspected heart attack because they are more specific for heart damage than other tests and remain high for a longer period of time.  Chest pain can be due to heart problems or other causes such as indigestion or a strain on the chest muscle. If the heart does not get enough additional oxygen during exercise, it causes chest pain. Inadequate flow of oxygen is usually due to a partial blockage of the blood vessels caused by gradual build up of fat (atherosclerosis, or hardening of the arteries). This type of pain is felt during exercise and stops when a persons rests and is called angina.

Sometimes, a small blood clot forms in a blood vessel, causing chest pain while a person is at rest, or which continues after exercise stops. If the blood clot clears, the chest pain will stop; this condition is called 'unstable angina'. In unstable angina, any damaged heart cells will release troponin.

People who have unstable angina and an abnormal troponin, but normal CK, CK–MB, have a higher risk of having a heart attack or other serious heart problem in the next few months. Many doctors now check troponin in patients with unstable angina to identify those who may benefit from such treatments as angioplasty (using a balloon to open a blocked heart blood vessel) or heart bypass surgery.

The troponin test will usually be carried out when a patient with a suspected heart attack comes to hospital. Different testing protocols are used by different hospitals – some hospitals will measure troponin on arrival at the emergency department and may repeat the test at 6 and 12 hours later while others may only measure a single 12 hour post admission level (to rule out a heart attack). It is sometimes requested with other tests such as CK, CK–MB.

In patients with stable angina, a troponin test may be requested if the pain get worse, if it appears when the patient is resting, and/or if the pain does not get better following treatment.  These are all signs that the angina is becoming unstable, which increases the risk of a heart attack or other serious heart problems in the near future.

Normally, troponin levels are so low that they can not be measured.

Even a small rise in troponin may indicate some damage to the heart. When a patient has a large increase in troponin concentration in the blood, then it is highly likely that the patient has had a heart attack or some other form of heart damage. When a patient with chest pain and/or known stable angina has a normal troponin level, then it is likely that their heart has not been damaged.

Troponin values can remain high for 1–2 weeks after a heart attack.  The test is not generally affected by damage to other muscles, so muscle injections, accidents or drugs that cause damage muscle do not normally affect troponin levels.

Increased troponin concentrations should not be used by themselves to diagnose or rule out a heart attack. A physical examination, clinical history and ECG are also important. Some people who have a heart attack will have a normal troponin concentration, and some people with an increased troponin concentrations have no obvious heart damage. Troponin levels may also be increased with short term or long term inflammation of the heart (myocarditis), congestive heart failure, severe infections, kidney disease, and some chronic inflammatory conditions of muscles and skin.