The 0/1-hour troponin pathway was safe but did not speed discharge

Design

Pragmatic, randomised, non-inferiority implementation trial

Population

3,543 patients with suspected acute coronary syndrome in two English emergency departments

Primary outcome

Discharge within 4 hours; 30-day MACE sensitivity among discharged patients

Effect

Discharged ≤4 h 21.8% vs 19.2% (P=0.07); sensitivity 93.7% vs 89.5%, non-inferior

MACROS2, published in May, randomised 3,543 patients with suspected acute coronary syndrome in two emergency departments in north-west England to the ESC 0/1-hour high-sensitivity troponin T pathway or a 0/3-hour pathway. Outcomes were adjudicated with a separate troponin I to avoid bias.

Discharge within four hours was 21.8% vs 19.2% (P=0.07). The 0/1-hour pathway was non-inferior for safety among discharged patients: sensitivity for 30-day major adverse cardiac events was 93.7% vs 89.5%. Laboratory turnaround from sample to result was a median 81 minutes, which ate much of the time the shorter interval should have saved.

The lesson is about systems, not assays. Moving to a 0/1-hour protocol without fixing laboratory turnaround, bed flow and decision-making will not shorten stays. Both pathways missed more events than observational studies had suggested, which argues for clear safety-netting at discharge.

• Measure your laboratory's sample-to-result time before expecting a 0/1-hour pathway to shorten stays.
• The 0/1-hour pathway was at least as safe as 0/3 hours for patients sent home.
• Sensitivity was about 90–94% in practice, lower than observational studies implied.
• Give discharged patients explicit safety-net advice and a clear route back.
• Point-of-care high-sensitivity assays may be needed to realise the time saving.

Why it matters

Departments have adopted the 0/1-hour pathway expecting faster discharge, and this randomised test shows the bottleneck lies elsewhere.

Don't overread it

The discharge difference was not significant, but this was two English departments — systems with faster laboratories may see more gain.

The statistics, in plain English

Non-inferiority means the 0/1-hour pathway was shown not to be worse than 0/3 hours by more than a 3% margin in sensitivity. The two sensitivity intervals overlap widely, so neither pathway was clearly better at catching events.

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