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Lab Manual for UCSF Clinical Laboratories

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TROPONIN I

Item Value
Available Stat? Yes
Test code TRPI
Performed by? Chemistry
Sendout? no
Price range $$
In House Availability Routine: 7 days.
STAT: 24 hours/7 days.
Principle The Siemens Centaur assay is a three-site sandwich immunoassay using direct chemiluminometric technology.
Interpretation Troponin is the contractile regulatory protein complex of striated muscle and consists of 3 components: troponin-C, troponin-T, and troponin-I. Cardiac troponin-I is one of those isotypes which is found in the heart. Following a myocardial infarction, cardiac troponin-I becomes abnormal 4 - 8 hours following onset of chest pain, peaks at 12-16 hours and remains elevated for 5 - 9 days.

Recent consensus statements are unequivocal in finding improved cardiac specificity and sensitivity for cardiac troponin-I compared to CKMB for the detection of myocardial injury. Recently, the European Society of Cardiology and American College of Cardiology have redefined the criteria for diagnosis of AMI, putting increasing emphasis on serum/plasma biomarkers. These guidelines established a troponin cutoff for AMI diagnosis at the 99th percentile of a healthy population. Because existing commercial assays are insufficiently sensitive to reliably detect troponin in normal individuals, a working group of the ESC/ACC has recommended that the cutoff be established at a troponin value that exhibits a 10% interday imprecision. Note that values between the 99th percentile and the 10% CV AMI cutoff concentration can occur in patients with acute coronary syndromes and may be associated with an increased risk of coronary events. All values should be interpreted in the context of the patient's clinical presentation.
Container type green top tube
Amount to Collect 1 mL
Collection Instructions Serum (gold or red top tube) is not acceptable.
Sample type Plasma
Normal range
99th Percentile: < 0.04 ng/mL (< 0.04 mcg/L)
cutoff for AMI diagnosis: 0.35 ng/mL (0.35 mcg/L)


NOTE: The Laboratory will call the first result above 0.34 ng/mL for Emergency Department patients.
Stability 24 hrs at 2-8°C;
1 month at -20°C.
Interferences 1. Auto- (rheumatoid factor) and heterophile antibodies in human serum can react with reagent immunoglobulins, interfering with in vitro immunoassays. Patients routinely exposed to animals or to animal serum products can be prone to this interference. Anomalous values may be observed. The most common, although not exclusive, interference seen in immunometric ("two-site," or "sandwich") assays is a spuriously high value. Results inconsistent with clinical findings or previous laboratory values can be investigated by the laboratory for this phenomenon. Call the Clinical Chemistry Laboratory Medicine Resident (x65527, pager 415-443-2311).

2. A paradoxical, false low result may rarely occur when patient samples with extremely high concentrations of peptide/protein analytes (e.g. AFP, hCG, PSA, etc.) are measured by immunometric ("two-site," or "sandwich") assays. For example, a true value of 3,000,000 U/L could be reported as < 5 or 21 U/L. This phenomenon is called the "high dose hook effect." Results inconsistent with clinical findings or previous laboratory values can be investigated by the laboratory for this phenomenon. Call the Clinical Chemistry Laboratory Medicine Resident (x65527, pager 415-443-2311).
References 1. Bayer 118282 Rev. E, 2002-04. Siemens Medical Solutions Diagnostics, Malvern, PA.

2. Myocardial infarction redefined - a consensus document of the Joint European Society of Cardiology/American College of Cardiology Committee for the redefinition of myocardial infarction. J Am Coll Cardiol 2000;36:959-969.

3. Braunwald E, Antman EM, Beasley JW, Califf RM, Cheitlin MD, Hochman JS, et al. ACC/AHA guidelines for the management of patients with unstable angina and non-ST segment elevation myocardial infarction: executive summary and recommendations. A report of the American College of Cardiology/American Heart Association task force on practice guidelines (Committee on the Management of Patients with Unstable Angina). Circulation 2000;102:1193-1209.

4. Wu AHB, Apple FS, Gibler WB, Jesse RL, Warshaw MM, Valdes R Jr. National Academy of Clinical Biochemistry Standards of Laboratory Practice: Recommendations for use of cardiac markers in coronary artery diseases. Clin Chem 1999; 45:1104-21.

5. Joint European Society of Cardiology/American College of Cardiology Committee. Myocardial infarction redefined - a consensus document of the joint European Society of Cardiology/American College of Cardiology Committee for the redefinition of myocardial infarction. J Am Coll Cardiol 2000;36:959-69.

6. Jaffe AS, Ravkilde J, Roberts R, Naslund U, Apple FS, Galvani M, Katus H. It's time for a change to a troponin standard. Circulation 2000;102:1216-20.

7. Melanson, SEF, Morrow, DA, Jarolim, P. Earlier detection of a myocardial injury in a preliminary evaluation using a new troponin I assay with improved sensitivity. Am J Clin Pathol, 2007; 128:282-286.

CPT coding 84484
Last Updated 6/18/2011 8:26:10 AM
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