Ngaio Troponin Test

SUMMARY AND EXPLANATION OF THE TEST

The heart releases troponin into the blood following an injury, such as a heart attack. When a myocardial infarction (MI) occurs in the hypo perfused region of the myocardium, oxygen can no longer be supplied to the cells in the region. Cell death is inevitable if oxygen is not restored within 10-15 minutes and will result in the release of certain proteins from within cytoplasm in to the blood stream.

Some proteins are exclusive to and predominant in the cardiac muscle cells; they can function as cardiac markers and be detected in the blood specimens of AMI patients by specialized immunoassays. cTnI is one of the biochemical markers widely used for the determination of AMI in chest pain patients.

Troponin is a contractile regulatory protein complex found in skeletal and cardiac muscle. The troponin complex consists of three distinctive polypeptide components, troponin I (TnI), troponin T (TnT), and troponin C (TnC), and plays a fundamental role in the transmission of intracellular calcium signal actin-myosin interaction.

TnC of cardiac tissues is identical to that in skeletal tissues, but TnI and TnT of cardiac isoforms are different from those of skeletal isoforms, which enables the development of cardiac specific antibodies.

Moreover, cTnI levels become elevated in the blood as a result of myocardial injury or necrosis. Therefore, cTnI is used as an aid in the diagnosis of myocardial infarction.

Studies on the release kinetics indicate that cTnI is not early marker of myocardial necrosis. It appears in serum within 3-6 hours after symptom onset, similar to the release of CK-MB. However, cTnI remains elevated for 4-9 days post-AMI.

In addition to its utility in diagnosis, elevated cTnI levels convey prognostic information and have been shown to identify patients having an increased risk of death.