A 55-year-old man presents 18 hours after onset of crushing chest pain. Serum troponin-I is markedly elevated. Which property of cardiac troponin-I makes it MOST superior to CK-MB as a biomarker for myocardial injury?
- A It is expressed exclusively in cardiac muscle and has no significant skeletal isoform ✓
- B It rises faster than CK-MB within the first 2 hours
- C It is cleared by the kidney and hence normalises faster
- D It activates the coagulation cascade and predicts thrombus size
Correct answer: A. It is expressed exclusively in cardiac muscle and has no significant skeletal isoform
Explanation
Cardiac troponin-I is encoded by a gene distinct from the skeletal-muscle troponin-I gene, giving it absolute cardiac specificity; CK-MB is also expressed in regenerating skeletal muscle and can be falsely elevated in rhabdomyolysis or marathon runners. cTnI rises at 4–6 hours (not faster than CK-MB at 2 hours), and its prolonged window (up to 10–14 days) is a diagnostic advantage. It has no role in coagulation.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.