Which statement about cardiac troponin I (cTnI) in acute myocardial infarction is false?

Which statement about cardiac troponin I (cTnI) in acute myocardial infarction is false?

• A. Increase above reference interval seen in 3 to 6 hours
• B. Measured initially and serially in 3- to 6-hour intervals
• C. Remains elevated 5 to 10 days
• D. Expressed in regenerating and diseased skeletal muscle and cardiac muscle disorders

Answer: (D)

Cardiac troponin I is a cardiac-specific protein that rises in the blood after myocardial injury. After an acute myocardial infarction, it becomes detectable within a few hours, typically within 3 to 6 hours. Clinicians often measure it initially and then repeat testing at 3- to 6-hour intervals to watch for a rising or falling pattern that confirms ongoing injury and helps time the event. Because troponin remains elevated for several days, cTnI can stay above the reference range for about 5 to 10 days (sometimes longer, depending on the extent of damage). This persistence is why troponin is useful for diagnosing myocardial infarction even if the patient presents later. Regarding expression in skeletal muscle, cTnI is not expressed in healthy skeletal muscle. Skeletal muscle uses different troponin I isoforms. The cardiac-specific assay is designed to detect cardiac troponin I, and skeletal muscle disease or regenerating skeletal muscle does not produce cTnI detectable by these tests. Therefore, the statement claiming expression of cTnI in regenerating or diseased skeletal muscle is not correct.

Cardiac troponin I is a cardiac-specific protein that rises in the blood after myocardial injury. After an acute myocardial infarction, it becomes detectable within a few hours, typically within 3 to 6 hours. Clinicians often measure it initially and then repeat testing at 3- to 6-hour intervals to watch for a rising or falling pattern that confirms ongoing injury and helps time the event.

Because troponin remains elevated for several days, cTnI can stay above the reference range for about 5 to 10 days (sometimes longer, depending on the extent of damage). This persistence is why troponin is useful for diagnosing myocardial infarction even if the patient presents later.

Regarding expression in skeletal muscle, cTnI is not expressed in healthy skeletal muscle. Skeletal muscle uses different troponin I isoforms. The cardiac-specific assay is designed to detect cardiac troponin I, and skeletal muscle disease or regenerating skeletal muscle does not produce cTnI detectable by these tests. Therefore, the statement claiming expression of cTnI in regenerating or diseased skeletal muscle is not correct.