COMPARISON OF CARDIAC TROPONIN-I AND LACTATE-DEHYDROGENASE ISOENZYMESFOR THE LATE DIAGNOSIS OF MYOCARDIAL INJURY

Cardiac troponin I (cTnI) is a highly specific marker that is elevated in the blood for several days following myocardial infarction, The la ctate dehydrogenase (LD) isoenzyme 1 to isoenzyme 2 ratio (LD1/LD2) is the established marker for the late diagnosis of myocardial infarctio n, In this study, the sensitivity of cardiac troponin I (cTnI) and LD1 /LD2 were compared as late markers of myocardial injury over a 5-day p eriod in 36 patients admitted with a diagnosis of myocardial infarctio n to the coronary care unit. Over this period, the sensitivity of cTnI was significantly greater than that of LD1/LD2 (P < .05). The concurr ent elevation of both cardiac markers of the five day period range fro m 53.1% to 79.4%. However, this low concordance was largely due to an LD1/LD2 <1 in the presence of an increased cTnI. The average discordan ce over the 5-day period was 29.5%. Because cardiac troponin I(cTnI) h as greater sensitivity than lactate dehydrogenase isoenzymes for delay ed diagnosis of myocardial injury and is a more cost-effective test, t he authors recommend it as a test of choice in this setting.