Use of enzyme immunoassay for measurement of skeletal troponin-I utilizing isoform-specific monoclonal antibodies

Objectives: To determine the serum level of fast skeletal troponin I (fsTnI) resulting from skeletal muscle damage, we have developed a sensitive two-site enzyme immunoassay to measure skeletal troponin I. Design and Methods: Twelve monoclonal antibodies were raised against human fsTnI. Of these antibodies, 8 were fsTnI-specific and the remaining 4 reacted with both skeletal and cardiac troponin I (cTnI). Two monoclonals were utilized for a development of this fsTnI immunoassay. Standards were made with purified recombinant human fsTnI for the range of 0–25 μg/mL. Results: Total assay variance (CV) ranged from 1.7% to 9.6%. The upper limit of the normal reference range was established as 0.2 μg/L by determining fsTnI concentration in sera of 108 healthy donors without evidence of muscle damage. Purified human cTnI up to 500 μg/L and cTnI-positive clinical serum samples yielded negative results in the fsTnI assay. The serum levels of fsTnI were determined in trauma patients, patients with chronic degenerative muscle disease, and marathon runners. In the study populations, the serum levels of fsTnI were correlated with other biochemical markers that are traditionally used to monitor striated muscle damage. Conclusions: In the present preliminary studies, measuring the serum levels of fsTnI in patients with various forms of muscle damage is more accurate than using the classical non muscle-specific biochemical markers.