The sensitivity of cardiac markers: an evidence-based approach

The aim of this study was to determine whether, using an evidence-based app roach, the results of the papers found in the literature are valid and suff iciently scientifically rigorous to be used to definitely address the probl em of cardiac marker sensitivity in detection of acute myocardial infarctio n. In particular, the diagnostic sensitivities of myoglobin, creatine kinas e (CK)-MB isoenzyme, determined as mass concentration, OK-MB isoforms, and of the two cardiac troponins, troponin I and troponin T,were reviewed using a priori formulated inclusion/exclusion criteria for judging the eligibili ty of studies to be included in the analysis. A clear final message derived from this systematic analysis is the unacceptably poor diagnostic sensitiv ity of all evaluated markers at patient admission, with substantial failure rate to rule out myocardial infarction at this time. Myoglobin is at prese nt the most sensitive of the markers studied for excluding early AMI with a n optimum timing of sampling at patient presentation and approximately 4 h later. However, this marker cannot be used by itself as a proportion of pat ients admitted to the hospital with a late infarction could be missed. The early rate of rise of OK-MB mass and troponin T is similar. Maximum sensiti vity of these two parameters is achieved by the analysis of a second sample 6 to 12 h after admission. Additional larger studies are needed to address the question which troponin shows earlier release after myocardial damage, and to clarify the role of OK-MB isoforms as a possible early marker of my ocardial infarction.