• Differential diagnosis of elevated cardiac troponin (cTn).
• To distinguish acute myocardial infarction (AMI) from chronic troponin elevations (e.g., chronic heart failure, end-stage renal disease).
• Particularly useful when the baseline troponin is already above the 99th percentile upper reference limit (URL).

AMI is characterized by dynamic rising and/or falling patterns of troponin due to acute myocyte necrosis and release of the protein into the bloodstream. Chronic injury (Type II injury) results in a steady-state elevation of troponin without significant kinetic changes.

• If Baseline ≤ 99th percentile URL: A relative increase of ≥ 50% or a significant absolute increase is often used.
• If Baseline > 99th percentile URL: A relative change (rise or fall) of ≥ 20% or a specific absolute change (e.g., > 10 ng/L over 3 hours) is considered diagnostic for acute injury.

A falling troponin is as clinically significant as a rising one. It suggests the peak of the injury has passed (e.g., post-reperfusion or late presentation of MI).