Troponin I ELISA
The Calbiotech cTnI ELISA is intended for the quantitative determination of cardiac Troponin I in human serum or plasma. Measurement of Troponin I values are useful in the evaluation of acute myocardial infarction (AMI).
Troponin is the inhibitory or contractile regulating protein complex of striated muscle. It is located periodically along the thin filament of the muscle and consists of three distinct proteins: troponin I, troponin C, and troponin T. Likewise, the troponin I subunit exists in three separate isoforms; two in fasttwitch and slow-twitch skeletal muscle fibers, and one in cardiac muscle. The cardiac isoform (cTnI) is about 40% dissimilar, has a molecular weight of 22,500 daltons, Cardiac troponin I (cTnI) has been useful in the differential diagnosis of patients presenting to Emergency Departments (ED) with chest pain 18-20. Myocardial infarction is diagnosed when blood levels of sensitive and specific biomarkers, such as cardiac troponin, the MB isoenzyme of creatine kinase (CK-MB), and myoglobin, are increased in a clinical setting of acute ischemia. The most recently described and preferred biomarker for myocardial damage is cardiac troponin (I or T). The cardiac troponins exhibit myocardial tissue specificity and high sensitivity. The level of cTnI remains elevated for a much longer period of time (6-10 days), thus providing for a longer window of detection of cardiac injury. Normal levels of cTn I in the blood are very low. After the onset of an AMI, cTnI levels increase substantially and are measurable in serum within 4 to 6 hours, with peak concentrations reached in approximately 12 to 24 hours after infarction. The cTnI Enzyme Immunoassay provides a rapid, sensitive, and reliable assay for the quantitative measurement of cardiac-specific troponin I. The antibodies developed for the test will determine a minimal concentration of 1.0 ng/ml, and theres no cross-reactivity with human cardiac or skeletal troponin T or I.
The cTnI ELISA test is based on the principle of a solid phase ELISA. The assay system utilizes four unique monoclonal antibodies directed against distinct antigenic determinants on the molecule. Three mouse monoclonal anti-troponin I antibodies are used for solid phase immobilization (on the microtiter wells). The fourth antibody is in the antibody-enzyme conjugate solution. The test sample is allowed to react simultaneously with the four antibodies, resulting in the troponin I molecules being sandwiched between the solid phase and enzyme-linked antibodies. After a 90-minute incubation at room temperature, the wells are washed with water to remove unbound-labeled antibodies. A solution of (TMB) is added and incubated for 20 minutes, resulting in the development of a blue color. The color development is stopped with the addition of Stop Solution changing the color to yellow. The concentration of troponin I is directly proportional to the color intensity of the test sample. Absorbance is measured spectrophotometrically at 450 nm.
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