Which of the following laboratory tests is the most sensitive and specific for diagnosing acute

Which of the following laboratory tests is the most sensitive and specific for diagnosing acute

Which of the following laboratory tests is the most sensitive and specific for diagnosing acute myocardial infarction (AMI) within the first 3-6 hours of symptom onset?

A. Creatine kinase-MB (CK-MB)

B. Troponin I

C. Myoglobin

D. Lactate dehydrogenase (LDH)

Answer: B

Explanation: Troponin I is a cardiac-specific protein that rises within 3-6 hours of AMI, peaks at 12-24 hours, and remains elevated for 7-10 days. It has higher sensitivity and specificity than CK-MB (A, which peaks earlier but is less specific) and myoglobin (C, which rises earliest but is not cardiac-specific). LDH rises later (12-24 hours) and is less specific (D is incorrect).