The choice of the diagnostic biomarkers of acute coronary syndromes

Abstract

Cardiac markers have undergone an amazing transformation from asparatate aminotransferase (AST) and lactate dehydrogenase (LDH) to the three cardiac markers families available at present for routine use in Emergency Department for the evaluation of the chest discomfort: myoglobin, creatine kinase (CK) and the MB isoenzyme of CK (CK-MB), and the troponins I and T (cTnI and cTnT). Each of these has well known kinetics of release from dying myocardial cells and should be carefully applied to each patient as directed by timing of symptoms and presentation. Myoglobin has been touted as an early marker with a high negative predictive value but low specificity. CK and CK-MB represent the "gold standard" for the diagnosis of MI as defined by the WHO criteria. The toponins are cardiac-specific proteins with high degrees of both sensitivity and specificity for myocardial necrosis. These serum markers of necrosis have been well studied in high-risk groups with a high prevalence of AMI. Promising research has also proven benefit in lower-risk patients in the chest pain units. Inflammatory markers such as C-reactive protein (CRP) and markers of platelet such as P-selectin are currently being studied but have not yet been accepted for widespread use. Cardiac markers have proved extremely valuable for diagnosis, risk stratification and treatment of patients in the emergency setting. However, the ideal cardiac marker evaluation protocol varies between institutions, laboratories, patient's populations, and resource availability. Specific marker regimens should be tailored to meet the objectives of diagnosis myocardial infarction and providing risk stratification. New tests are developed at a fast rate and the technology of existing test is continuously being improved. A rigorous evaluation process of diagnostic tests before introduction into clinical practice could not only reduce the number of unwanted clinical consequences related to misleading estimates of test accuracy, but also limit health care costs by preventing unnecessary testing. The evaluation of diagnostic tests is complex but analytical accuracy and diagnostic accuracy is recognized as two of the pillars. Earlier recognition of problems with the quality of reporting of randomized, controlled clinical trials resulted in the Consolited Standards of Reporting Trials (CONSORT) Statement, on the basis of which a checklist of items that should be easily identified in the report of any study on diagnostic accuracy has been developed. The Standards for Reporting of Diagnostic Accuracy (STARD) group has tried to provide the evidence supporting the various components of the Statement. On the basis of these approach, the concept of Evidence- Based Laboratory Medicine (EBLM) should be taken seriously, therefore, for several reasons. First, we should all take pride in producing the best results possible to aid physicians in making diagnostic, prognostic, and treatment decisions. Second, the enormous increase in diagnostic testing is under scrutiny. Third, modern health services question whether laboratory tests offer good value for the money. Biochemical markers of myocardial injury are universally accepted as important for the diagnosis of patients with acute coronary syndromes. In addition to very well established biomarkers, many potential biomarkers are introduced as natriuretic peptides, cardiotonic steroids, cytokines, ischemia-modified albumin, free fatty acids, etc. and their significance and usefulness for acute coronary syndromes will be discussed, as well.