hs-Troponin 0/1-Hour Algorithm Interpreter
hs-Troponin 0/1-Hour Algorithm Interpreter
Apply the ESC 0 h/1 h algorithm to a baseline and one-hour high-sensitivity troponin, using the thresholds published for your own assay. It sorts patients into rule-out, rule-in and observe — it does not diagnose, and it never overrides clinical judgement.
hs-Troponin 0/1-Hour Algorithm
Assay + two troponins → triagehs-cTnT (Elecsys): baseline 18 ng/L, 1-hour 21 ng/L, chest pain onset over 3 hours ago
The ESC 0 h/1 h algorithm
Rule-in — 0 h at or above the high threshold; or the 1-hour change at or above its threshold
Observe — everything else
- the thresholds are assay-specific
- the rule-in value alone ranges from 40 ng/L on one platform to 120 ng/L on another. Applying one assay's numbers to another assay's result is the single most dangerous way to misuse this algorithm
- the 3-hour condition applies to one branch only
- the guideline permits rule-out at presentation on a very low value only if chest pain began more than 3 hours earlier. The 0 h/1 h algorithm itself applies to all patients irrespective of onset — the condition restricts the single-sample shortcut, not the whole pathway
- the delta is an absolute change
- in ng/L, not a percentage, and not a rise from a fixed baseline. A percentage change from a very low first value is unstable and is not what the algorithm uses
- it does not apply to STEMI
- a patient with ST elevation, or any indication for immediate invasive angiography, goes to the catheter laboratory. No troponin algorithm is run first and none should delay reperfusion
- rule-in is a triage category
- not a diagnosis of myocardial infarction. It identifies myocardial injury; infarction additionally requires evidence of ischaemia, and many non-ischaemic conditions produce the same numbers
Worked example
hs-cTnT (Elecsys): baseline 18 ng/L, 1-hour 21 ng/L, chest pain onset over 3 hours ago
18 ng/L is below the Elecsys rule-in threshold of 52, so no rule-in on the baseline
18 is not below the very-low threshold of 5, so the single-sample rule-out does not apply even though onset was over 3 hours ago
The 1-hour change is |21 − 18| = 3 ng/L, below the rule-in delta of 5
For rule-out the baseline must be below 12 and the change below 3. Neither holds: 18 is above 12, and a change of exactly 3 is not below 3
So this patient is in the observe zone — a further troponin at around 3 hours, an echocardiogram in most services, and a decision on the whole picture
Note how narrowly it fell there. A change of 2 ng/L instead of 3 still would not rule out, because the baseline of 18 is above the low threshold of 12. Both conditions have to hold
ESC 0 h/1 h thresholds, in ng/L
| Assay | Very low (0 h) | Low (0 h) | No 1 h change | High (0 h) | 1 h change |
|---|---|---|---|---|---|
| hs-cTnT (Elecsys, Roche) | < 5 | < 12 | < 3 | ≥ 52 | ≥ 5 |
| hs-cTnI (Architect, Abbott) | < 4 | < 5 | < 2 | ≥ 64 | ≥ 6 |
| hs-cTnI (Centaur, Siemens) | < 3 | < 6 | < 3 | ≥ 120 | ≥ 12 |
| hs-cTnI (Access, Beckman Coulter) | < 4 | < 5 | < 4 | ≥ 50 | ≥ 15 |
| hs-cTnI (Vitros, Ortho Clinical Diagnostics) | < 1 | < 2 | < 1 | ≥ 40 | ≥ 4 |
| hs-cTnI (Pathfast, LSI Medience) | < 3 | < 4 | < 3 | ≥ 90 | ≥ 20 |
| hs-cTnI (TriageTrue, Quidel) | < 4 | < 5 | < 3 | ≥ 60 | ≥ 8 |
What each outcome means, and what it does not
| Outcome | What it means | What it does not mean |
|---|---|---|
| Rule-out | NSTEMI is excluded, with a negative predictive value above 99% in validation cohorts | Coronary disease is excluded, or unstable angina is excluded. A typical exertional history still needs assessment |
| Observe | The algorithm does not classify this patient. Around a quarter land here | That the patient is low risk. A meaningful minority of the observe zone are having an infarction, and this is the group where a further troponin and an echocardiogram matter most |
| Rule-in | A high probability of acute myocardial injury, and a triage decision to admit and investigate | A diagnosis of myocardial infarction. Injury is not infarction, and myocarditis, pulmonary embolism, sepsis, arrhythmia and severe kidney disease all reach these values |
Three thresholds, one hour, and the zone in the middle
The ESC 0 h/1 h algorithm exists because most people who arrive with chest pain are not having a myocardial infarction, and the traditional six-hour troponin wait held all of them in the department to find that out. High-sensitivity assays detect myocardial injury within one to three hours of onset and measure reliably at concentrations that older assays could not see at all, which makes a one-hour decision possible. The algorithm takes a presentation sample, a second sample one hour later, and sorts patients into three groups: rule-out, rule-in, and observe.
Everything depends on using the right numbers. The thresholds are specific to the assay, and the spread between platforms is not small — the rule-in concentration ranges from 40 ng/L on one analyser to 120 ng/L on another, and the one-hour delta from 4 to 20 ng/L. Applying a remembered threshold from a different hospital, or a troponin I value against a troponin T algorithm, is the most dangerous single error available here. So is a unit error: these figures are ng/L, and a result reported in ng/mL or µg/L must be multiplied by a thousand first.
One condition is frequently misapplied. The guideline allows NSTEMI to be ruled out at presentation, on the very low baseline alone, only when chest pain began more than three hours before that sample — because a patient sampled during the first hour of an evolving infarction may not yet have released detectable troponin. But the guideline also states that the 0 h/1 h algorithm applies to all patients irrespective of chest pain onset. The three-hour condition restricts the single-sample shortcut; it does not gate the whole pathway. This page implements it that way.
The observe zone is where the real work is. Around a quarter of patients land there, it is not a low-risk group, and a meaningful minority of them are having an infarction. These patients need a further troponin at around three hours, an echocardiogram in most services, and a decision taken on the whole clinical picture. The algorithm is a triage instrument that should always be integrated with a detailed clinical assessment and a 12-lead ECG. It does not apply to a patient with ST elevation or any other indication for immediate invasive angiography — they go to the catheter laboratory, and nothing here should delay that. And no output of it is a decision: a rule-out in someone whose story is convincing is a reason to think harder, not a reason to discharge.
Frequently asked questions
What are the ESC 0/1-hour troponin cut-offs?
They differ by assay. For hs-cTnT on Elecsys, rule-out at a baseline under 5 ng/L (with chest pain onset over 3 hours earlier) or under 12 ng/L with a 1-hour change under 3 ng/L; rule-in at a baseline of 52 ng/L or above, or a 1-hour change of 5 ng/L or more. The table on this page gives all seven assay sets from the 2023 ESC guideline.
Can I use one assay's thresholds with another assay's result?
No, and this is the most dangerous misuse of the algorithm. The rule-in concentration ranges from 40 to 120 ng/L across the seven published assays and the 1-hour delta from 4 to 20 ng/L. Identify the assay your laboratory runs before applying any of these numbers.
Does the algorithm only work if chest pain started more than 3 hours ago?
No. That condition applies to one branch only — ruling out on a very low baseline at presentation, without a second sample. The guideline states the 0 h/1 h algorithm itself applies to all patients irrespective of chest pain onset, so an early presenter simply needs the 1-hour sample.
What does the observe zone mean?
That the algorithm cannot classify this patient. Around a quarter fall here and it is not a low-risk group — a meaningful minority are having a myocardial infarction. They need a further troponin at about 3 hours, an echocardiogram in most services, and a decision on the whole clinical picture rather than a discharge.
Does this algorithm apply to STEMI?
No. A patient with ST elevation, or any other indication for immediate invasive angiography, goes straight for reperfusion. The 0 h/1 h algorithm is for suspected non-ST-elevation acute coronary syndrome, and no troponin result should delay primary percutaneous coronary intervention.
Does a rule-in result mean a heart attack?
No. It is a triage category meaning a high probability of acute myocardial injury. Infarction additionally requires evidence of ischaemia from the history, the ECG, imaging or angiography, and myocarditis, pulmonary embolism, sepsis, tachyarrhythmia, heart failure and advanced kidney disease all produce values in the rule-in range.
Related calculators
References
- Byrne RA, Rossello X, Coughlan JJ, et al. 2023 ESC Guidelines for the management of acute coronary syndromes. Eur Heart J. 2023;44(38):3720–3826, with Supplementary Table S4 (assay-specific 0 h/1 h cut-offs).
- Reichlin T, Twerenbold R, Wildi K, et al. Prospective validation of a 1-hour algorithm to rule-out and rule-in acute myocardial infarction using a high-sensitivity cardiac troponin T assay. CMAJ. 2015;187(8):E243–E252.
- Twerenbold R, Neumann JT, Sörensen NA, et al. Prospective validation of the 0/1-h algorithm for early diagnosis of myocardial infarction. J Am Coll Cardiol. 2018;72(6):620–632.
- Joint ESC/ACC/AHA/WHF Task Force for the Universal Definition of Myocardial Infarction. Fifth Universal Definition of Myocardial Infarction (2026). Circulation. 2026. doi:10.1161/CIR.0000000000001477.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.