A 57-year-old man has just returned from an overseas trip and reports having had severe substernal chest pain 3 days ago. Which of the following is the most appropriate laboratory test to order for this patient?

Question

Quizplus · Accepted Answer

Troponin I is the most specific and sensitive marker for myocardial infarction and remains elevated for up to 10 days, making it the most appropriate test for detecting myocardial injury several days after the event.  Troponin I is now the method of choice for the laboratory diagnosis of MI. There is a detectable increase within 4 to 8 hours of the infarction and the peak level is reached within 12 to 16 hours. Levels do not return to baseline for 3 to 10 days making it an appropriate test for this patient who was 3 days postinfarction. Aspartate aminotransferase was the first serum enzyme marker used for the diagnosis of MI, but it has poor specificity and sensitivity compared to newer markers and is no longer used for this purpose Creatine kinase total is not used for the diagnosis of MI since the cardiac fraction (MB) can be overwhelmed by the presence of the skeletal muscle fraction. Creatine kinase-MB is still being used in some institutions but it returns to baseline in 2 to 3 days and would not be useful for this patient. Lactate dehydrogenase (LD1 fraction) returns to baseline later than creatine kinase but has been replaced by troponin I and is seldom used.

A 57-Year-Old Man Has Just Returned from an Overseas Trip