Test Catalog

Test ID: HSTNI    
Troponin I, High Sensitivity, Plasma

Useful For Suggests clinical disorders or settings where the test may be helpful

Excluding the diagnosis of acute coronary syndromes


Explaining troponin T elevations related to skeletal myopathy and/or assay interferences

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

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 and 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 Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Males > or =18 years: < or =20 ng/L

Females > or =18 years: < or =15 ng/L


Reference values have not been established for patients less than 18 years old.

Interpretation Provides information to assist in interpretation of the test results

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 Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

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, renal failure and pulmonary embolism.

Clinical Reference Recommendations for in-depth reading of a clinical nature

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 Mar 1;66(3):434-444