The use of biochemical markers for diagnosis of the acute coronary syndromes

It was recognized very early that the specificity of AST, LDH, and CK was not high for cardiac diseases, as injury to the liver and skeletal muscles and hemolysis produced falsely positive results. Thus the measurement of isoenzymes becomes important to improve the specificity of total enzyme measurements. Assays for CK and LD isoenzymes were initially developed using electrophoresis. Because this assay was time consuming and difficult to automate, imunooinhibition assays were soon developed. The development of immunoassay measurements enabled determination of the enzyme concentration which was not dependent on whether or not the enzyme was active. These "mass assays" also enabled the measurement of protein markers which are themselves not enzymes. This led to the investigation of many other markers for potential use in cardiac diseases. With changing clinical practices, cardiac markers are now needed to detect the presence of minor myocardial infarction in patients with unstable angina. Outcome studies have shown that patients with increased troponin are at high short-term risk for death and AMI. The success of new cardiac markers such as troponin is due to their high cardiac specificity and the existence of assays with low detection limits.