Prehospital risk stratification in suspected non-ST-segment elevation acute coronary syndrome with point-of-care troponin: an individual patient data meta-analysis

BACKGROUND: Emergency Medical Services (EMS) patients with chest pain are often suspected of having non-ST-elevation acute coronary syndrome (NSTE-ACS). Current risk stratification protocols for NSTE-ACS have limitations, leading to a lack of a well-organised prehospital diagnostic pathway. Recent studies have demonstrated that using clinical risk scores (CRS) including point-of-care (POC)-troponin in the EMS can improve prehospital diagnostic pathways for suspected NSTE-ACS. The primary aim of this systematic review and individual patient data meta-analysis was to assess safety of low-risk stratification for suspected NSTE-ACS patients in the prehospital setting. METHODS: Prospective studies using CRS or POC-troponin for risk stratification in suspected NSTE-ACS patients within the EMS setting were included. Safety was assessed using sensitivity and negative predictive value (NPV) for patients identified as low risk, based on CRS or POC-troponin measurement, for three different endpoints within 30 days: (1) all-cause mortality, (2) composite of mortality and/or acute myocardial infarction (AMI), (3) major adverse cardiac events (MACE). RESULTS: Of 1526 articles screened, 6 were included, comprising 5.239 patients, and all utilised CRS derived from the History, ECG, Age, Risk-factor and Troponin (HEART) score. The summary of low-risk CRS diagnostic performance predicted all-cause mortality with a sensitivity of 93.2% (83.5-98.1) and NPV of 99.8% (99.5-99.9); mortality and/or AMI with a sensitivity of 91.8% (83.0-96.2) and an NPV of 97.3% (89.9-99.3); and MACE with a sensitivity of 92.8% (88.7-95.5) and an NPV of 97.2% (92.1-99.0). Lowering the CRS cut-off value for identifying low-risk patients increased sensitivity and NPV but decreased the proportion of patients classified as low risk. CONCLUSION: In well-trained EMS systems, where prompt and accurate follow-up of low-risk patients is possible, HEART-derived CRS effectively identify patients with a very low risk of 30-day mortality and MACE. However, implementation in other healthcare systems requires additional validation, given the variations in healthcare structure, risk stratification processes and follow-up capabilities.