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HelpMayo Test ID HSTNI Troponin I, High Sensitivity, Plasma
Specimen Required
Collection Container/Tube:
Preferred: Mint green top (lithium heparin gel)
Acceptable: Green top (lithium heparin)
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions:
1. Plasma gel tube should be centrifuged within 2 hours of collection.
2. Green-top tube should be centrifuged, and the plasma aliquoted into a plastic vial within 2 hours of collection.
Useful For
Excluding the diagnosis of acute coronary syndromes
Explaining troponin T elevations related to skeletal myopathy and/or assay interferences
Method Name
Electrochemiluminescence Immunoassay
Reporting Name
Troponin I, High Sensitivity, PSpecimen Type
PlasmaSpecimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Plasma | Frozen (preferred) | 180 days | |
| Refrigerated | 48 hours | ||
| Ambient | 4 hours |
Reject Due To
| Gross hemolysis | Reject |
Clinical Information
Troponin is a complex that regulates the contraction of striated muscle. It consists of 3 subunits (C, T, and I) that are located periodically along the thin filament of the myofibrils. Troponin I inhibits actomyosin ATPase.
Troponin I is an inhibitory protein and exhibits in 3 isoforms: cardiac muscle, slow-twitch skeletal muscle, and fast-twitch skeletal muscle. The cardiac form of troponin I has 31 amino acid residues on its N-terminal, which allow for specific polyclonal and monoclonal antibody development, as they are not present in the skeletal forms. The cardiac specificity of this isoform improves the accuracy of diagnosis in patients with acute or chronic skeletal muscle injury and possible concomitant myocardial injury.
Troponin I is the only troponin isotope present in the myocardium and is not expressed during any developmental stage in skeletal muscle. Troponin I is released into the bloodstream within hours of the onset of symptoms of myocardial infarction or ischemic damage. It can be detected at 3 to 6 hours following onset of chest pain, with peak concentrations at 12 to 16 hours, and remains elevated for 5 to 9 days.
Reference Values
Males ≥18 years: ≤20 ng/L
Females ≥18 years: ≤15 ng/L
Reference values have not been established for patients younger than 18 years old.
Interpretation
Elevations in cardiac troponin T (cTnT) can be due to skeletal muscle disease and not cardiac disease in certain circumstances. One way to unmask such elevations is to measure cardiac troponin I (cTnI), which will be normal in that situation. In addition, at times there are interferences that can cause spurious increases or decreases in cTnT values. Conceptually, these same interferences can occur with cTnI but in any given case, the likelihood of having both assays be confounded in that way is highly unusual. Thus, potential false-positive results would be unmasked by a normal cTnI and false-negative results by an elevated value.
Cautions
A troponin value above the upper reference limit (99th percentile) value is not always indicative of myocardial infarction. Other conditions resulting in myocardial cell damage can contribute to elevated cardiac troponin I levels. These conditions include, but are not limited to, myocarditis, cardiac surgery, angina, unstable angina, congestive heart failure, and noncardiac-related causes, such as, kidney failure and pulmonary embolism.
Clinical Reference
Apple FS, Wu AHB, Sandoval Y, et al. Sex-specific 99th percentile upper reference limits for high sensitivity cardiac troponin assays derived using a universal sample bank. Clin Chem. 2020;66(3):434-444
Method Description
The Access hsTnI (high sensitivity troponin I) assay is a two-site immunoenzymatic (sandwich) assay. Monoclonal anti-cTnI (cardiac troponin I) antibody conjugated to alkaline phosphatase is added to a reaction vessel along with a surfactant-containing buffer and sample. After a short incubation, paramagnetic particles coated with monoclonal anti-cTnI antibody are added. The human cTnI binds to the anti-cTnI antibody on the solid phase, while the anti-cTnI antibody-alkaline phosphatase conjugate reacts with different antigenic sites on the cTnI molecules. After incubation in a reaction vessel, materials bound to the solid phase are held in a magnetic field while unbound materials are washed away. Then, the chemiluminescent substrate is added to the vessel and light generated by the reaction is measured with a luminometer. The light production is directly proportional to the concentration of cTnI in the sample. The amount of analyte in the sample is determined from a stored, multi-point calibration curve.(Package insert: ACCESS hsTnI. Beckman Coulter; 10/2021)
Day(s) Performed
Monday, Wednesday, Friday
Report Available
2 to 3 daysSpecimen Retention Time
7 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
84484
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| HSTNI | Troponin I, High Sensitivity, P | 89579-7 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| HSTNI | Troponin I, High Sensitivity, P | 89579-7 |