Serum troponin testing is the most widely used and most definitive marker of myocyte injury.
What is troponin?
The troponin class of proteins are all contractile proteins that regulate muscle contraction; they work with calcium ions and another protein called tropomyosin. There are three types of troponin proteins:
- Troponin C – Calcium-binding component
- Troponin I – Inhibitory component
- Troponin T – Tropomyosin-binding component
Troponins are found in cardiac muscle and slow-twitch and fast-twitch skeletal muscles.
- Troponin C is found in both cardiac and skeletal muscle in the same form.
- Troponin I has a specific form found in cardiac muscle – cTnI.
- Troponin T also has a cardiac-specific form – cTnT.
Unlike the CK enzymes, troponins, specifically cTnI and cTnT, are much more specific to the myocardial tissue, making them superior markers for cardiac testing. If cTnI or cTnT are detected in the serum, we can be fairly certain myocardial damage is present. Consequently, CK-MB testing has been replaced with troponin testing. Many argue that CK-MB testing should, in fact, now be considered obsolete. The majority of large academic hospitals no longer perform CK-MB testing.
