Lab Test

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Troponin I

Cardiac Troponin, TnI

Test Codes

EPIC: LAB7028, Beaker: TROPG, Antrim: 16950
(Inpatient Orders Only)

Department

Chemistry

Specimen Collection Criteria

Preferred Sample:  One Light Green (Mint) Top Lithium Heparin PST (Lithium Heparin plasma gel separator tube) or Dark Green top Lithium Heparin tube. (Minimum Whole Blood: 4.0 mL)

Do NOT use Gold-top Serum Separator (SST) tubes, Dark Green top Sodium Heparin tubes, Red-top serum tubes, or Lavender-top EDTA tubes or microtainers.

Physician Office/Draw Specimen Preparation

Invert PST tubes 8 times for proper mixing of heparin anticoagulant, then centrifuge immediately to separate plasma from cells, 1300 x g for 10 minutes (e.g., Drucker horizon mini E centrifuge). Refrigerate (2-8°C or 36-46°F) the centrifuged PST tube. (Minimum: 1.0 mL plasma)

For Dark Green top Lithium Heparin tubes: Invert 8 times for proper mixing of heparin anticoagulant, then centrifuge immediately to separate plasma from cells and aliquot plasma into a labeled tube. Refrigerate (2-8°C or 36-46°F) the labeled aliquot tube.

Preparation for Courier Transport

Transport:

  • Centrifuged PST tube, refrigerated (2-8°C or 36-46°F). (Minimum: 1.0 mL plasma)
  • Labeled aliquot tube, refrigerated (2-8°C or 36-46°F). (Minimum: 1.0 mL plasma)

Rejection Criteria

  • Light Green-top PST tubes with plasma not separated from cells within two hours of collection.
  • Dark Green-top Lithium Heparin tubes not spun; plasma not in labeled aliquot tubes or not refrigerated.
  • Specimens collected in microtainer tubes.
  • Specimens collected in inappropriate collection tubes.
  • Specimens not collected and processed as indicated.
  • Grossly hemolyzed specimens (Farmington Hills Only).
  • Outreach specimens.

In-Lab Processing

Centrifuge PST tubes or dark green top lithium heparin tubes to separate plasma from cells. For STAT troponin orders, centrifuge PST tubes or dark green top lithium heparin tubes at 4000 x g for 3 minutes (e.g., StatSpin Express 4 centrifuge). For routine analysis, centrifuge specimens at 1300 x g for 5 minutes. Dark green top lithium heparin tubes should be centrifuged and plasma should be separated from cells and aliquoted  prior to testing. Specimens should be free of particulate matter. Deliver immediately to the appropriate testing station or add aliquoted labeled plasma sample to the line.

Storage

Specimen Stability for Testing:

Centrifuged PST Tubes
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): 48 hours
Frozen (-20°C/-4°F or below): Unacceptable

Plasma Specimens (Pour-Overs)
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): 48 hours
Frozen (-20°C/-4°F or below): 8 weeks

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Laboratory

Taylor Chemistry Laboratory
Trenton Chemistry Laboratory
Wayne Chemistry Laboratory 

Performed

Sunday – Saturday, 24 hours a day.
STAT results available within 1 hour of receipt in the Laboratory.
Routine results available within 4 hours.

Reference Range

 Normal   ≤ 0.03 ng/mL.
 Indeterminate  0.04 – 0.29 ng/mL.
 Suggestive of Myocardial Damage  ≥ 0.30 ng/mL.


Samples with results greater than 50 ng/mL will not be diluted and will be reported as "greater than 50.00 ng/mL."

Test Methodology

Chemiluminescence Immunoassay.

Interpretation

Patients routinely exposed to animals or to animal serum products may develop heterophilic antibodies that can interfere with test results. Erroneous findings may also be obtained from samples taken from patients who have been treated with monoclonal mouse antibodies or have received them for diagnostic purposes.

Studies have shown that in the absence of an apparent acute coronary syndrome, an elevated level of either troponin T or troponin I in end stage renal disease is associated with an increased risk of mortality.

Clinical Utility

Increases in troponin I occur in acute coronary syndromes with myocardial necrosis as well as myocardial infarction with ST elevation. Troponin I is detectable about 3-4 hours after the occurrence of cardiac symptoms. Following acute myocardial ischemia, troponin I remains in the serum for several days and can help to detect myocardial events that have occurred up to 7-10 days earlier.

Increases are also associated with direct myocardial damage (e.g., myocarditis, pericarditis, contusion, cardioversion), myocardial strain (e.g., CHF, pulmonary hypertension, pulmonary embolus) and demand ischemia (e.g., sepsis, hypotension, atrial fibrillation). Troponin may also be elevated in entities such as renal failure, intracranial hemorrhage and amyloidosis. The mechanism for the latter elevations is unclear. An elevated troponin level is a predictor for poor outcome regardless of its cause.

CPT Codes

84484
LOINC: 10839-9

Contacts

Last Updated

1/10/2024

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