What troponin assay and values are recommended for excluding myocardial infarction (MI) in chest pain lasting >3 hours, and is a second result needed?

From the Guidelines

For chest pain lasting >3 hours, a high-sensitivity cardiac troponin (hs-cTn) assay is recommended to exclude myocardial infarction, with a single hs-cTn result below the assay's limit of detection (typically <5 ng/L) effectively ruling out MI if symptoms began >3 hours before testing, as supported by the 2022 ACC expert consensus decision pathway 1. The use of high-sensitivity cardiac troponin assays allows for earlier and more accurate diagnosis of myocardial infarction.

• A single hs-cTn result below the assay's limit of detection can effectively rule out MI in patients with symptoms lasting more than 3 hours.
• If the initial troponin is detectable but below the 99th percentile upper reference limit, a second measurement should be taken 1-3 hours later to assess for a significant change.
• The negative predictive value of a single undetectable hs-cTn in patients with >3 hours of symptoms exceeds 99.5%, making it a reliable exclusion strategy, as noted in the 2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR guideline for the evaluation and diagnosis of chest pain 1.
• For conventional (non-high-sensitivity) troponin assays, serial measurements at 0 and 3-6 hours are still required regardless of symptom duration, as recommended by the 2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes 1. The 99th percentile upper reference limit is the recommended threshold for myocardial injury and diagnosis of MI, as stated in the 2022 ACC expert consensus decision pathway 1 and the Universal Definition of Myocardial Infarction 1.
• The use of high-sensitivity cardiac troponin assays with a validated 0/1h or 0/2h algorithm can help in the early rule-out of MI, as suggested by the 2022 ACC expert consensus decision pathway 1 and the 2015 ESC guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation 1.
• The High-STEACS pathway, which uses high-sensitivity troponin assays, has been validated in randomized controlled trials and can be used for early rule-out of MI, as noted in the 2022 ACC expert consensus decision pathway 1 and the 2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR guideline for the evaluation and diagnosis of chest pain 1.

From the Research

Troponin Assay and Values for Excluding Myocardial Infarction (MI)

• High-sensitivity troponin assays are recommended for excluding MI in patients with chest pain lasting >3 hours 2, 3, 4, 5, 6.
• The 99th percentile upper reference limit is commonly used as the threshold for ruling out MI 2, 3, 4, 6.
• A high-sensitivity troponin level below the 99th percentile at 6 hours or greater from symptom onset can safely rule out acute coronary syndrome in patients who do not meet rapid rule-out criteria 2.

Need for a Second Troponin Result

• A second troponin result may be needed to confirm the diagnosis or rule out MI, especially if the initial result is inconclusive or if the patient's symptoms persist 3, 4, 5, 6.
• The timing of the second troponin result can vary, but it is often recommended to be taken 2-3 hours after the initial result 3, 4, 5, 6.
• The use of a delta criterion (e.g., ≥20% change in troponin levels) can help improve the specificity of the troponin test, but may reduce sensitivity 3, 5.

Specific Troponin Assays and Thresholds

• The Roche high-sensitivity troponin T assay with a threshold of <12 ng/L at 0 hours and Δ <3 ng/L at 0 to 1 hours may be cost-effective for ruling out MI 6.
• The Beckman Coulter Access High Sensitivity Troponin I assay with a threshold of <4 ng/L at 0 hours or <5 ng/L and Δ <5 ng/L at 0 to 2 hours may be cost-effective for ruling out MI 6.
• The Siemens Healthcare Dimension Vista High-Sensitivity Troponin I assay with a threshold of <5 ng/L at 0 hours and Δ <2 ng/L at 0 to 1 hours may be cost-effective for ruling out MI 6.