Cardiac-specific immunoenzymometric assay of troponin I in the early phase of acute myocardial infarction.

The screening by immunoenzymometric assay (IEMA) of 784 monoclonal antibody (MAb) combinations resulted in the selection of an optimal pair of MAbs for measuring human cardiac troponin I (TnI). Using a one-step IEMA described here, we were able to detect TnI within the range of 0.2-20 micrograms/L in 30 min at room temperature. No cross-reactivity was observed with the skeletal isoforms of troponin up to a concentration of 500 micrograms/L. This assay was used to measure cardiac TnI in the plasma of 43 patients with acute myocardial infarction (AMI). TnI was detected relatively early after the onset of chest pain (4.3 +/- 2.1 h, mean +/- SD); the peak occurred after 12.2 +/- 4.6 h in a population that had undergone fibrinolysis. TnI disappearance was generally observed between 5 and 9 days after the onset of chest pain. No cardiac TnI could be detected in 145 healthy donors or in a control group of 6 patients (with skeletal damage or rhabdomyolysis). This assay allows a specific diagnosis of AMI in its early acute phase, with a high diagnostic specificity and sensitivity.