A radioimmunoassay for the measurement of human cardiac myosin light chains.

A double-antibody radioimmunoassay that specifically measures serum or urinary concentrations of human cardiac myosin light chains has been developed. The assay is both sensitive and specific for myosin light chain I. The antiserum used in the assay is capable of detecting 1--2 ng/ml of cardiac myosin light chain I and shows no cross-reaction to cardiac myosin, the heavy chains of myosin, actin, tropomyosin, or light chain II. Of 114 patients admitted to the Coronary Care Unit, 227 measurements obtained from 84 patients without myocardial infarction revealed that the serum light chain level of 2.0 +/- 0.18 ng/ml was not significantly different from that of a control group (2.1 +/- 0.17 ng/ml, n = 12). In contrast, 89 measurements from 30 patients with myocardial infarction evidence clinically, electrocardiographically, and by creatine phosphokinase determinations were found to have an average serum light chain I concentration of 10.9 +/- 1.39 ng/ml (P less than 0.001). Thus, the radioimmunoassay for human cardiac myosin light chain I provides a sensitive and specific marker for myocardial damage.

Clinical assessment of serum myosin light chains in the diagnosis of acute myocardial infarction.

Serum myosin light chain levels were quantitated with radioimmunoassay in patients admitted to the coronary care unit. In this study there were 29 patients with acute myocardial infarction, 84 with chest pain but without myocardial infarction and 5 with chest pain but with preexisting electrocardiographic abnormalities that could not be interpreted using standard criteria. Values for human cardiac light chains in normal human sera averaged less than 2 ng/ml, and values in the 84 patients without myocardial infarction fell into this category. The 29 patients with myocardial infarction all had elevated light chain concentrations (average 10.9 +/- 1.3 ng/ml; range 4 to 35 ng/ml). In this study there were no false positive or false negative results. Use of this assay has permitted separation of patients with and without myocardial infarction. The assay for cardiac light chains provides a biochemical marker of high sensitivity and specificity that is useful in the diagnosis of infarction.