Why has CK-MB mass testing become less common in modern practice?

• A. High-sensitivity troponin assays have largely replaced CK-MB mass testing.
• B. CK-MB mass testing is faster but less reliable.
• C. CK-MB mass testing is more expensive and unavailable.
• D. CK-MB mass testing requires invasive sampling.

Answer: (A)

High-sensitivity troponin assays have largely replaced CK-MB mass testing because troponin is highly specific to cardiac muscle and the high-sensitivity versions detect very small elevations, enabling earlier and more accurate identification of myocardial injury. This combination provides better diagnostic accuracy, faster rule-in/rule-out of acute coronary syndromes, and more reliable prognostic information. CK-MB mass can rise in non-cardiac conditions and is less sensitive in the early hours after injury, making it less reliable for timing and specificity. While CK-MB mass testing isn’t entirely obsolete in all settings, modern practice favor its cardiac-specific counterpart due to superior performance and guideline support.