Which of the following is not associated with the assessment of an acute myocardial infarction?

• A. Elevated serum CK-MB level
• B. Elevated serum troponin level
• C. Abnormal serum alkaline phosphatase isoenzyme pattern
• D. Blood collected upon presentation and serially in 3- to 6-hour intervals

Answer: (C)

In evaluating a possible acute myocardial infarction, the focus is on cardiac-specific biomarkers and the timing of their appearance. Troponin (I or T) is the most sensitive and specific marker for myocardial injury and remains elevated for days after an infarct, while CK-MB rises with myocardial necrosis and helps indicate infarct size when used with troponin. Because the biomarker pattern over time is important, blood samples are taken at presentation and then serially every 3 to 6 hours to document a rise and fall consistent with an acute event. An abnormal alkaline phosphatase isoenzyme pattern, however, is not used to assess myocardial infarction; ALP isoenzymes reflect bone, liver, or biliary conditions and do not indicate cardiac injury.