Validity and reliability of the South African Triage Scale in prehospital providers

Background: The South African Triage Scale (SATS) is a validated in-hospital triage tool that has been innovatively adopted for use in the prehospital setting by Western Cape Government (WCG) Emergency Medical Services (EMS) in South Africa. The performance of SATS by EMS providers has not been formally assessed. The study sought to assess the validity and reliability of SATS when used by WCG EMS prehospital providers for single-patient triage.

Methods: This is a prospective, assessment-based validation study among WCG EMS providers from March to September 2017 in Cape Town, South Africa. Participants completed an assessment containing 50 clinical vignettes by calculating the three components - triage early warning score (TEWS), discriminators (pre-defined clinical conditions), and a final SATS triage color. Responses were scored against gold standard answers. Validity was assessed by calculating over- and under-triage rates compared to gold standard. Inter-rater reliability was assessed by calculating agreement among EMS providers' responses.

Results: A total of 102 EMS providers completed the assessment. The final SATS triage color was accurately determined in 56.5%, under-triaged in 29.5%, and over-triaged in 13.1% of vignette responses. TEWS was calculated correctly in 42.6% of vignettes, under-calculated in 45.0% and over-calculated in 10.9%. Discriminators were correctly identified in only 58.8% of vignettes. There was substantial inter-rater and gold standard agreement for both the TEWS component and final SATS color, but there was lower inter-rater agreement for clinical discriminators.

Conclusion: This is the first assessment of SATS as used by EMS providers for prehospital triage. We found that SATS generally under-performed as a triage tool, mainly due to the clinical discriminators. We found good inter-rater reliability, but poor validity. The under-triage rate of 30% was higher than previous reports from the in-hospital setting. The over-triage rate of 13% was acceptable. Further clinically-based and qualitative studies are needed.

Trial registration: Not applicable.