What delta in troponin levels is considered significant for a non-ST-elevation myocardial infarction (NSTEMI)?

From the Guidelines

A significant delta in troponin levels for diagnosing NSTEMI is typically a rise and/or fall of at least 20% from baseline, with at least one value above the 99th percentile upper reference limit, as recommended by the most recent guidelines 1. When considering the diagnosis of NSTEMI, it is crucial to evaluate the change in troponin levels over time, rather than a single measurement.

• The 2021 ESC guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation suggest that a rise or fall in troponin levels of at least 20% from baseline, with at least one value above the 99th percentile upper reference limit, is indicative of NSTEMI 1.
• High-sensitivity troponin assays may require smaller percentage changes compared to conventional assays, with a change of 50-100% within 3 hours for very low baseline values, or 20% for baseline values above the upper reference limit considered significant.
• Serial measurements of troponin levels are essential, typically taken at presentation and 3-6 hours later, to distinguish acute myocardial injury from chronic elevation and improve diagnostic accuracy.
• The interpretation of troponin levels should always be made in the clinical context, considering the patient's symptoms, ECG findings, and risk factors, as troponin elevation can occur in conditions other than myocardial infarction, such as renal failure, sepsis, or pulmonary embolism.
• The 2019 recommendations for institutions transitioning to high-sensitivity troponin testing provide guidance on the use of accelerated diagnostic protocols, including the 0/1h, 0/2h, and 0/3h protocols, to rule out or rule in MI or place patients in an observational zone 1.
• The 2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes emphasizes the importance of considering serial changes in troponin levels for the diagnosis of MI, with a troponin value above the 99th percentile of the upper reference level required, and evidence for a serial increase or decrease ≥20% if the initial value is elevated 1.

From the Research

Delta in Troponin Levels for NSTEMI

• The delta in troponin levels considered significant for a non-ST-elevation myocardial infarction (NSTEMI) is a topic of ongoing research, with various studies suggesting different thresholds 2, 3, 4, 5, 6.
• A study published in 2015 found that an absolute delta of 0.01 or 0.02 ng/mL in troponin I levels performed better than a relative delta of 20% within 3-6 hours for diagnosing NSTEMI 2.
• Another study from 2013 found that absolute delta changes in high-sensitivity cardiac troponin T (hs-cTnT) were more accurate than relative delta changes for diagnosing NSTEMI, with an area under the receiver operating characteristic curve (AUC) of 0.89 versus 0.69 3.
• The use of small changes in troponin T levels to predict benefit from an early invasive strategy in patients with unstable angina and NSTEMI has also been explored, with one study finding that even small elevations in troponin I and T identify high-risk patients who derive a large clinical benefit from an early invasive strategy 4.
• However, another study found that small changes in troponin T levels are common in patients with NSTEMI and are linked to higher mortality, suggesting that a small troponin T change may not be useful to exclude NSTEMI 5.
• A high-sensitivity cardiac troponin T assay has been shown to increase the number of NSTEMI diagnoses and enable earlier detection of evolving NSTEMI, with a delta change of >20% or a ROC-optimized value within 3 or 6 hours yielding high specificity and sensitivity 6.

Key Findings

• Absolute delta changes in troponin levels may be more accurate than relative delta changes for diagnosing NSTEMI 2, 3.
• Small changes in troponin T levels are common in patients with NSTEMI and are linked to higher mortality 5.
• High-sensitivity cardiac troponin T assays can increase the number of NSTEMI diagnoses and enable earlier detection of evolving NSTEMI 6.
• The optimal delta in troponin levels for diagnosing NSTEMI remains a topic of ongoing research and debate 2, 3, 4, 5, 6.