Troponin I Quantitative

TPIOG

Lithium Heparin Plasma (Green Top Tube)

0.5 mL

Serum (Gold Top Tube)

This test is for random Troponin I measurement.  For measurement of Troponin I at Onset, 3 hours, 6 hours, and 12 hours after presentation, order ROMI for a ROMI Panel, which stands for Rule Out Myocardial Injury.  All 4 Troponin I

Lithium Heparin Plasma (Green Top) or Serum (Gold or Red Top) Tube

Room Temperature or Refrigeration

Room Temperature - 2 hours; Refrigerated - 7 days

Hemolysis, Turbidity, Quantity Not Sufficient, IV contamination

Daily upon receipt

Upon completion of analysis

For troubleshooting purposes, if the cTnI result is inconsistent with the clinical picture and is persistently elevated, the sample should be tested for the presence of heterophilic antibodies. These antibodies may be present in the blood samples from individuals regularly exposed to animals or who have been treated with animal serum products. Samples from patients receiving preparations of mouse monoclonal antibodies for therapy or diagnosis may contain Human Anti-Mouse Antibodies (HAMA). Such samples may show either falsely elevated or falsely depressed values when tested with this method. Streptokinase may interfere negatively with the predicted concentration of cTnI. Care should be taken when interpreting cTnI results after administration of streptokinase.

Reference Range:    < 0.034 ng/mL

Interpretative Data:

0.034 ng/mL or less:      Negative; repeat testing as clinically indicated.
0.034 - 0.12 ng/mL:        Suspicious for myocardial injury. Serial measurements may be necessary to confirm or exclude the diagnosis of acute coronary syndrome.
0.12 ng/ml:                      Consistent with myocardial injury.

*Changes in results should be interpreted based on method.

Troponin I (TnI) is a protein normally found in muscle tissue that, in conjunction with Troponin T and Troponin C, regulates the calcium dependent interaction of actin and myosin.  Three isotypes of TnI have been identified: one associated with fast-twitch skeletal muscle, one with slow-twitch skeletal muscle and one with cardiac muscle.  The cardiac form has an additional 31 amino acid residues at the N terminus and is the only troponin isoform present in the myocardium.  Clinical studies have demonstrated that cardiac Troponin I (cTnI) is detectable in the bloodstream 4–6 hours after an acute myocardial infarct (AMI) and remains elevated for several days thereafter.  Thus, cTnI elevation covers the diagnostic windows of both creatine kinase-MB (CK-MB) and lactate dehydrogenase.  Further studies have indicated that cTnI has a higher clinical specificity for myocardial injury than does CK-MB.  Other conditions resulting in myocardial cell damage can contribute to elevated cTnI levels. Published studies have documented that these conditions include, but are not limited to, sepsis, congestive heart failure, hypertension with left ventricular hypertrophy, hemodynamic compromise, myocarditis, mechanical injury including cardiac surgery, defibrillation and cardiac toxins such as anthracyclines.  Factors such as these should be considered when interpreting results from any cTnI test method.

Because of its cardiac specificity and sensitivity, cTnI has been used as a reliable marker in evaluating patients with unstable angina and non-ST segment elevation acute coronary syndrome (ACS).  Previous clinical studies of patients with ACS have shown that minor increases in cTnI values provide important prognostic information about the short and long term risk of death. Ultimately, the assessment of the prognosis can be useful in identifying patients most likely to benefit from specific therapeutic interventions.