Trending High-Sensitivity Cardiac Troponin in Acute Chest Pain
Use the 0- and 1-hour ESC algorithm as your first-line approach: obtain blood at presentation (0 h) and exactly 1 hour later, then apply assay-specific cutoffs for both absolute values and delta changes to rule-out or rule-in myocardial infarction. 1
Algorithm Selection and Timing
The 2021 European Society of Cardiology guidelines designate the 0/1-hour protocol as the best option for hs-cTn trending, with the 0/2-hour protocol as the second-best alternative. 1 The 2022 American College of Cardiology consensus acknowledges multiple validated pathways but notes the 0/1-hour algorithm takes advantage of superior assay sensitivity and precision while ruling out the largest proportion of patients. 1
Blood Draw Timing Requirements
- Draw the first sample immediately at presentation (time 0) regardless of symptom duration. 2
- Draw the second sample at exactly 1 hour after the first draw when using the 0/1-hour algorithm—timing precision is critical to algorithm validity. 1
- If your institution cannot reliably obtain 1-hour samples, use the 0/2-hour algorithm instead, which is equally complex but more practical for some centers. 1
ESC 0/1-Hour Algorithm: Three-Pathway Approach
The algorithm stratifies patients into three groups using assay-specific cutoffs for absolute troponin concentrations and delta changes:
Rule-Out Pathway (Low Risk)
Patients meet rule-out criteria when both conditions are satisfied: 1
- Very low baseline hs-cTn at 0 hours (assay-specific thresholds: <5 ng/L for Roche hs-cTnT, <4 ng/L for Abbott hs-cTnI, <3 ng/L for Siemens hs-cTnI), OR
- Low baseline hs-cTn at 0 hours (<12 ng/L for Roche, <5 ng/L for Abbott, <6 ng/L for Siemens) AND minimal 1-hour delta (<3 ng/L for Roche, <2 ng/L for Abbott, <3 ng/L for Siemens)
This pathway achieves a negative predictive value exceeding 99% for myocardial infarction in validation cohorts. 1 Patients in this category can be safely discharged from the emergency department with outpatient follow-up. 1
Critical caveat: The very-low baseline rule-out applies only if chest pain onset occurred >3 hours before presentation—earlier presenters require the full 0- and 1-hour serial assessment. 1, 2
Rule-In Pathway (High Risk)
Patients meet rule-in criteria when either condition is present: 1
- High baseline hs-cTn at 0 hours (≥52 ng/L for Roche, ≥64 ng/L for Abbott, ≥120 ng/L for Siemens), OR
- Significant 1-hour delta (≥5 ng/L for Roche, ≥6 ng/L for Abbott, ≥12 ng/L for Siemens) regardless of baseline value
The positive predictive value for myocardial infarction in the rule-in group is approximately 75%. 1 Most rule-in patients without MI have conditions requiring invasive coronary angiography or cardiac MRI (Takotsubo syndrome, myocarditis), so admission to a coronary care unit and early angiography are appropriate. 1
Observation Zone (Intermediate Risk)
Patients who meet neither rule-out nor rule-in criteria fall into the observation zone and require additional testing: 1
- Repeat hs-cTn at 3 hours from presentation
- Perform risk stratification with clinical scores (HEART, TIMI)
- Consider provocative testing (stress imaging, coronary CT angiography) if serial troponins remain in the observation range
Alternative Protocols When 0/1-Hour Is Not Feasible
0/2-Hour Algorithm
Identical three-pathway logic as 0/1-hour but with the second draw at 2 hours. 1 This protocol is better for very early presenters (symptom onset <2 hours) because it allows more time for troponin release, reducing false-negative results on the declining limb of late-presenting infarctions. 1
0/3-Hour Algorithm
Use a single hs-cTn <99th percentile if symptoms began >6 hours ago and the patient is now pain-free; otherwise, require both 0- and 3-hour values <99th percentile. 1 This approach has lower sensitivity and negative predictive value than 0/1-hour or 0/2-hour protocols and rules out fewer patients. 1 The 2021 ESC guidelines note that three recent large studies show the 0/3-hour algorithm balances efficacy and safety less favorably than the 0/1-hour protocol. 1
Assay-Specific Cutoffs for the 0/1-Hour Algorithm
You must use the validated thresholds for your institution's specific troponin assay—cutoffs are not interchangeable: 1
| Assay | Very Low (0 h) | Low (0 h) | No Delta (1 h) | High (0 h) | Delta (1 h) |
|---|---|---|---|---|---|
| Roche hs-cTnT | <5 ng/L | <12 ng/L | <3 ng/L | ≥52 ng/L | ≥5 ng/L |
| Abbott hs-cTnI | <4 ng/L | <5 ng/L | <2 ng/L | ≥64 ng/L | ≥6 ng/L |
| Siemens hs-cTnI | <3 ng/L | <6 ng/L | <3 ng/L | ≥120 ng/L | ≥12 ng/L |
Common Pitfalls and How to Avoid Them
Timing Errors
Never use emergency department arrival time as "time 0" if the exact blood draw time is documented—the algorithm requires precise 1-hour intervals between samples, not approximate times. 1 A sample drawn at 55 minutes or 75 minutes invalidates the algorithm's validated cutoffs.
Early Presenters
Do not apply the single very-low troponin rule-out to patients presenting <3 hours from symptom onset—troponin may not yet be detectable even in evolving MI. 1, 2 These patients require the full serial 0- and 1-hour assessment.
Late Presenters on the Declining Curve
The 0/1-hour algorithm may miss late-presenting MI when troponin is on the flat portion of a declining curve (e.g., patient presents 18 hours after symptom onset with troponin of 45 ng/L at 0 h and 43 ng/L at 1 h). 1 In patients with symptom onset >12 hours ago, consider extending observation and repeating troponin at 3–6 hours to capture the full kinetic pattern. 2
Non-ACS Troponin Elevation
Troponin elevation is non-specific—heart failure, pulmonary embolism, myocarditis, renal failure, and sepsis all elevate troponin. 1, 2 The rule-in pathway identifies myocardial injury, not necessarily acute coronary syndrome. Integrate ECG findings, echocardiography, and clinical context to differentiate ischemic from non-ischemic causes. 1
Chronic Troponin Elevation
Patients with chronic kidney disease, heart failure, or stable coronary disease often have baseline troponin above the 99th percentile. 2 In these patients, serial trend matters more than absolute value—a change <20% does not meet the diagnostic threshold for acute injury. 1, 2
Implementation in Clinical Practice
- Hospitals should adopt a standardized chest-pain protocol specifying troponin sampling intervals according to assay type (conventional vs. high-sensitivity). 2
- Central laboratory turnaround time for troponin results must be ≤1 hour to enable timely decision-making with the 0/1-hour algorithm. 2
- Real-world implementation studies, including one randomized controlled trial, confirm the very high safety and efficacy of the ESC 0/1-hour algorithm when applied in routine emergency department practice. 1