How reliable is the Canadian Triage and Acuity Scale (CTAS) for prioritizing emergency department patients, and what measures can improve its inter‑rater agreement?

Reliability of the Canadian Triage and Acuity Scale

The Canadian Triage and Acuity Scale (CTAS) demonstrates moderate to good reliability with inter-rater agreement ranging from kappa 0.46-0.77, and its reliability can be improved through structured training programs, standardized application of first-order modifiers, and integration with electronic health record systems. 1, 2, 3

Evidence for CTAS Reliability

Overall Performance Metrics

The CTAS system shows variable but generally acceptable reliability across different settings and user groups:

• Inter-rater reliability among emergency department nurses ranges from moderate (kappa 0.46 unweighted) to good (kappa 0.71-0.77 weighted), with exact or near-perfect agreement (within one triage level) occurring 84-90% of the time 1, 4, 3

• Intra-rater reliability is consistently strong, with kappa values of 0.87 for both senior and junior nurses when re-triaging the same scenarios 2

• The American Heart Association and American College of Physicians recognize CTAS as a validated screening tool for identifying critically ill patients, supporting its use alongside other evidence-based triage systems 5

Factors Affecting Reliability

Application of newer guideline revisions shows lower reliability than established criteria. The 2008 CTAS first-order modifiers demonstrated lower inter-rater agreement (kappa 0.50) compared to scenarios using the older 2004 guidelines (kappa 0.73), suggesting that newer modifications require enhanced training and standardization 1

Experience level has minimal impact on reliability. Both senior and junior nurses demonstrate similar intra-rater agreement (kappa 0.87), indicating that the scale itself provides adequate structure for consistent application across experience levels 2

Prehospital application by paramedics shows moderate agreement with emergency department nurse triage scores (kappa 0.44-0.45), with 84.3% exact or within-one-level concordance, demonstrating feasibility for pre-hospital implementation 4

Strategies to Improve Inter-Rater Agreement

Structured Training Programs

• Focus training on first-order modifiers and recent guideline updates, as these show the lowest reliability (kappa 0.50) and represent the greatest opportunity for improvement 1

• Implement scenario-based training using standardized case presentations to improve consistency in applying CTAS criteria across different clinical presentations 1, 3

• Provide regular refresher training, as the moderate concordance (57.6% exact agreement) indicates ongoing educational needs even among experienced triage nurses 3

System-Level Interventions

• Integrate CTAS into electronic health records to improve workflow, documentation, and standardization of triage decisions, as recommended by the American College of Physicians 5

• Standardize the use of presenting complaint terminology with the Canadian Emergency Department Information System (CEDIS) list, which achieved 90.1% concordance (kappa 0.80) in structured implementation 1

• Implement quality assurance programs with regular auditing of triage decisions and feedback to individual providers to maintain reliability over time 1, 4

Clinical Application Protocols

For stroke patients specifically, CTAS demonstrates effective stratification when applied systematically: most suspected strokes are appropriately triaged as CTAS Level 2, while those with compromised airway, breathing, or cardiovascular function are escalated to Level 1 6, 7

For pediatric patients, use the Pediatric Canadian Triage Acuity Scale (P-CTAS) with the same level structure, as this maintains reliability while accounting for age-specific physiologic parameters 6, 7

Common Pitfalls and How to Avoid Them

• Avoid inconsistent application of first-order modifiers (pain severity, bleeding, mechanism of injury) by creating decision support tools or quick reference guides that standardize their use 1

• Do not rely solely on initial impressions—the moderate inter-rater reliability (kappa 0.44-0.46) between paramedics and nurses highlights the importance of reassessment upon ED arrival 4

• Recognize that CTAS is not designed for mass casualty incidents—switch to color-coded systems (Red/Yellow/Green/Black) during resource-limited situations rather than attempting to adapt standard CTAS protocols 5, 8

• Document triage rationale clearly, as only 57.6% exact concordance among experienced nurses indicates significant variability that requires transparent decision-making for quality improvement 3

International Applicability

CTAS demonstrates good reliability when implemented outside Canada, with inter-rater agreement of kappa 0.77 between senior and junior nurses in Saudi Arabia, suggesting the scale's structure provides adequate guidance across different healthcare systems and cultural contexts 2