From the Guidelines
A significant change in troponin levels, often referred to as a "dynamic change," is typically defined as a rise or fall of at least 20% from the baseline value when the baseline is elevated above the 99th percentile upper reference limit, as recommended by the 2014 AHA/ACC guideline for the management of patients with non-st-elevation acute coronary syndromes 1. To determine the significance of troponin changes, it is essential to consider the initial troponin value and the percentage change over time.
- For troponin values above the 99th percentile upper reference level, a serial increase or decrease of ≥20% is required to indicate acute myocardial necrosis 1.
- For troponin values below or close to the 99th percentile, a change of ≥3 standard deviations of the variation around the initial value is indicative of acute myocardial necrosis, as determined by the individual laboratory 1. The specific delta values can vary depending on the particular troponin assay being used, as different laboratories may have different reference ranges and analytical precision 1. These changes should be evaluated within an appropriate timeframe, usually over 3-6 hours, to assess for acute myocardial injury, as suggested by the 2014 AHA/ACC guideline 1. The biological and analytical variability of troponin measurements necessitates these percentage-based cutoffs rather than absolute value changes. When interpreting troponin changes, it's crucial to consider the clinical context, as some conditions like renal failure or chronic heart failure can cause persistent troponin elevations without acute coronary syndromes 1. High-sensitivity troponin assays may require different criteria for significant changes, such as a change of at least 50% from a normal baseline or 20% from an elevated baseline 1. Point-of-care troponin values may provide initial diagnostic information, although their sensitivity is substantially below that of central laboratory methods, and rigorous quantitative assay standardization is needed for routine diagnosis 1.
From the Research
Troponin Change Requirements
To determine how much troponin must change to be considered dynamic, several studies have investigated the optimal thresholds for diagnosing acute myocardial infarction (AMI). The key findings are:
- A study published in 2011 2 found that a dynamic change (δ) of ≥20% in high-sensitivity troponin T (hs-TnT) improved diagnostic specificity, but decreased sensitivity.
- Another study from 2015 3 compared absolute and relative changes in troponin I and found that an absolute delta of 0.01 or 0.02 ng/mL performed better than a relative delta of ≥20% at various time intervals.
- A 2008 study 4 used a 20% increment between two cardiac troponin I measurements to diagnose MI, but found that only 23.2% of episodes met this criterion.
- Research from 2013 5 suggested that small changes in troponin T levels are common in patients with non-ST-segment elevation myocardial infarction (NSTEMI) and are linked to higher mortality.
- A 2017 study 6 found that a 2-hour troponin test with no significant delta troponin rise had a negative predictive value of 98.7% for high-risk patients with suspected acute coronary syndrome.
Key Findings
Some of the main points to consider are:
- The optimal threshold for troponin change is not universally agreed upon, with different studies suggesting absolute or relative changes.
- A ≥20% change in troponin levels is often used as a criterion for diagnosing AMI, but this may not be suitable for all patients.
- Small changes in troponin T levels can be associated with higher mortality in patients with NSTEMI.
- The use of high-sensitivity troponin assays may improve diagnostic accuracy, but the optimal thresholds for these assays are still being researched.
- Further studies are needed to determine the safest and most effective approach to diagnosing AMI using troponin levels.
Troponin Thresholds
Some of the troponin thresholds mentioned in the studies are: