troponins (Cardiac-specific troponin T [cTnT], Cardiac-specific troponin I [cTnI], High-sensitivity troponin [hsTnT, hs-cTn])
المؤلف:
Kathleen Deska Pagana, Timothy J. Pagana, Theresa Noel Pagana.
المصدر:
Mosbys diagnostic and laboratory test reference
الجزء والصفحة:
15th edition , p901-903
2025-09-27
375
Type of test Blood
Normal findings
Cardiac troponin T: < 0.1 ng/Ml
Cardiac troponin I: < 0.03 ng/mL
hsTnT :
< 14 ng/L for women
< 22 ng/L for men
Test explanation and related physiology
Cardiac troponins are important biochemical markers for cardiac disease. This test is used to assist in the evaluation of patients with suspected acute coronary ischemic syndromes. In addition to improving the diagnosis of acute ischemic disorders, troponins are also valuable for early risk stratification in patients with unstable angina. They can be used to predict the likelihood of future cardiac events. There are two cardiac-specific troponins: cTnT and cTnI.
Because of their extraordinarily high specificity for myocardial cell injury, cardiac troponins are very helpful in the evaluation of patients with chest pain. Their use is similar to that of creatine kinase-MB (CK-MB). However, cardiac troponins have several advantages over CK-MB. Cardiac troponins are more specific for cardiac muscle injury. CK-MB can be elevated in severe skeletal muscle injury, brain or lung injury, or renal failure. Cardiac troponins will nearly always be normal in noncardiac muscle diseases. Cardiac troponins become elevated sooner and remain elevated longer than CK-MB. This expands the time window of opportunity for diagnosis and thrombolytic treatment of myocardial injury. Finally, cTnT and cTnI are more sensitive to muscle injury than CK-MB. That is most important in evaluating patients with chest pain.
Cardiac troponins become elevated as early as 2 to 3 hours after myocardial injury. Typically, 2 to 3 sets of troponins over the course of a day (every 3-6 hours) are required to indicate myocardial infarction. Levels of cTnI may remain elevated for 7 to 10 days after myocardial infarction, and cTnT levels may remain elevated for up to 14 days. High sensitivity (hs)TnT rep resents an important advance with added sensitivity for cardiac myocyte necrosis. hsTnT assays detect concentrations of troponins at much lower concentrations, thereby detecting infarction earlier in the process (as early as 90 minutes). hsTnT speeds the triage of patients with suspected myocardial infarction.
Cardiac troponins are used in the following cardiac clinical situations:
• Evaluation of patient with unstable angina. If cardiac troponins are normal, no myocardial injury has occurred, and there will be no lasting cardiac dysfunction. If cardiac troponins are elevated, muscle injury has occurred. Revascularization may be indicated because this latter group is at great risk for a subsequent cardiac event (infarction or sudden death).
• Detection of reperfusion associated with coronary recanalization. A washout, or second peak of cardiac troponin levels, accurately indicates reperfusion by way of recanalization or coronary angioplasty.
• Estimation of myocardial infarction size. Late (4 weeks) cardiac troponin levels are inversely related to left ventricular ejection fraction.
• Detection of perioperative myocardial infarction. Cardiac troponins are not affected by skeletal muscle injury.
• Evaluation of the severity of pulmonary emboli. Elevated levels may indicate more severe disease and the need for thrombolytic therapy.
• Congestive heart failure. Persistently elevated troponins indicate continued ventricular strain.
Elevations of troponin T do not necessarily indicate the presence of an ischemic mechanism. Many other disease states are associated with elevations of troponin T via mechanisms different from those that cause injury in patients with acute coronary syndromes. These include cardiac trauma (e.g., contusion, ablation, or pacing), congestive heart failure, hypertension, hypotension (often with arrhythmias), pulmonary embolism, renal failure, and myocarditis. Interfering factors
• Severe skeletal muscle injury may cause false elevation of cTnT.
• Troponin T levels are falsely elevated in dialysis patients.
Procedure and patient care
• See inside front cover for Routine Blood Testing.
• Fasting: no
• Blood tube commonly used: yellow
* Discuss with the patient the need and reason for frequent venipuncture in diagnosing myocardial infarction.
• After the initial blood sample, blood is collected 12 hours later followed by daily testing for 3 to 5 days and possibly weekly for 5 to 6 weeks.
• Record the exact time and date of venipuncture on each laboratory slip. This aids in the interpretation of the temporal pat tern of enzyme elevations.
• If a qualitative immunoassay is to be done at the bedside, whole blood is obtained in a micropipette and placed in the sample well of the testing device. A red or purple color in the read zone indicates that 0.2 ng/mL or more of cardiac troponin is present in the patient’s blood.
Abnormal findings
Increased levels
- Myocardial injury
- Myocardial infarction
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