Test Directory

Immunoassay for the in vitro quantitative determination of cardiac troponin T (cTnT) in lithium heparin plasma. The immunoassay is intended to aid in the diagnosis of myocardial infarction.

Specimen Type: Plasma

Collection Container: Green Top (Lithium Heparin)

Desired Specimen Volume: 1 mL

1. Collect a green top (lithium heparin) tube via venipuncture.

1. Separate plasma from cells.
2. Transfer 1 mL of plasma to a LabCorp PP transpak frozen purple tube. Label as Li-Heparin plasma.
3. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin (also termed as vitamin B7 or B8, vitamin H, or coenzyme R). It is recommended to ask all patients who may be indicated for this test about biotin supplementation. Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.

Transport to the laboratory frozen. 

• Sample other than lithium heparin plasma

See patient report.

For diagnostic purposes, the results should always be assessed in conjunction with the patient’s medical history, clinical examination and other findings.

The Universal Definition of AMI takes into consideration the ESC/ACC/AHA/WHF definition recommending the detection of a rise and/or fall of cardiac troponin in the clinical setting with at least one value above the 99th percentile upper reference limit. Due to the release kinetics of cardiac troponin T, an initial test result may not be definitive in diagnosing MI. Serial cardiac troponin measurements are suggested.

Troponins are released during the process of myocyte necrosis. While they are cardiac-specific, they are not specific for MI, and detectable levels may be seen in other disease states that involve the heart muscle (e.g. arrhythmia, acute aortic syndrome, acute heart failure, hypertensive crisis, myocarditis, pericarditis, pulmonary embolism and Takotsubo cardiomyopathy), so that ACC/ESC/AHA guidelines and the Universal Definition of MI recommend serial sampling with a rise or fall in troponin to distinguish between acute and chronic cTn elevations.

A number of factors other than AMI are associated with elevated values. Published clinical studies have shown elevations of cardiac troponin T in patients with myocardial injury, as seen in stable or unstable angina, heart failure, myocarditis, pulmonary embolism, pericarditis, arrhythmias, cardiac contusions, and cardiac transplants. Elevations are also notable in patients with rhabdomyolysis and polymyositis.

Samples showing visible signs of hemolysis may cause interference. Falsely depressed results are obtained when using samples with hemoglobin concentrations > 0.1 g/dL.

For assays using antibodies, the possibility exists for interference by heterophileantibodies in the patient’s sample. Patients who have been regularly exposed to animals or have received immunotherapy or diagnostic procedures using immunoglobulin or immunoglobulin fragments may produce antibodies, e.g. HAMA, that interfere with immunoassays. Carefully evaluate the results of patients suspected of having these antibodies.

In rare cases, interference due to extremely high titers of antibodies to analyte‐specific antibodies, streptavidin or ruthenium can occur. The reagent has been formulated to minimize this effect.

Samples should not be taken from patients receiving therapy with high biotin doses (i.e.> 5 mg/day) until at least 8 hours following the last biotin administration.

• Cardiac Troponin T