Background:

Mass casualty incidents (MCIs) create a critical imbalance between medical needs and available resources, requiring rapid, reliable, and ethically grounded triage. In Sweden, the absence of a unified national system prompted a government-mandated initiative to develop a standardized mass casualty triage algorithm with broad professional acceptance and strong scientific underpinning.

Objective:

To develop, implement, and evaluate a national mass casualty triage system for Sweden that is evidence-based, user-centred, rapid to apply, and applicable across prehospital and intrahospital settings and multiple responder groups.

Results:

The system was developed through literature reviews, expert interviews, and a structured Delphi consensus process, followed by iterative user‑centred design. The final algorithm is adapted from the SALT framework and formalised as the Swedish Model Uniform Core Criteria (SMUCC). It includes five triage categories: Red (Immediate), Yellow (Urgent), Green (Non‑urgent), Blue/White (Expectant/Wait), and Black (Lifeless). The algorithm relies on binary clinical assessments (breathing, life‑threatening bleeding, purposeful movement) and is designed to be completed in approximately 60 seconds per casualty. Evaluation in large‑scale simulation exercises demonstrated a mean triage time of 36–42 seconds, overall accuracy of 83.7%, sensitivity of 77%, specificity of 86%, positive predictive value of 91%, and negative predictive value of 84%. User surveys showed high perceived usability, clarity, and suitability for national implementation.

Conclusions:

The Swedish national mass casualty triage system provides a standardized, validated, and operationally feasible framework for prioritising casualties during MCIs. Its strong consensus foundation, favourable performance metrics, and high user acceptance support national adoption. Continued refinement through training, integration with existing systems, and long‑term evaluation is recommended.