Validity of the Paediatric Canadian Triage Acuity Scale in a Tertiary Hospital: An Analysis of Severity Markers' Variability.

With the increasing influx of patients and frequent overcrowding, the adoption of a valid triage system, capable of distinguishing patients who need urgent care, from those who can wait safely is paramount. Hence, the aim of this study is to evaluate the validity of the Paediatric Canadian Triage and Acuity Scale (PaedCTAS) in a Portuguese tertiary hospital. Furthermore, we aim to study the performance and appropriateness of the different surrogate severity markers to validate triage. This is a retrospective study considering all visits to the hospital's Paediatric Emergency Department (PED) between 2014 and 2019. This study considers cut-offs on all triage levels for dichotomization in order to calculate validity measures e.g. sensitivity, specificity and likelihood ratios, ROC curves; using hospital admission, admission to intensive care and the use of resources as outcomes/markers of severity. Over the study period there were 0.2% visits triaged as Level 1, 5.7% as Level 2, 39.4% as Level 3, 50.5% as Level 4, 4.2% as Level 5, from a total of 452,815 PED visits. The area under ROC curve was 0.96, 0.71, 0.76, 0.78, 0.59 for the surrogate markers: "Admitted to intensive care"; "Admitted to intermediate care"; "Admitted to hospital"; "Investigations performed in the PED" and "Uses PED resources", respectively. The association found between triage levels and the surrogate markers of severity suggests that the PedCTAS is highly valid. Different surrogate outcome markers convey different degrees of severity, hence different degrees of urgency. Therefore, the cut-offs to calculate validation measures and the thresholds of such measures should be chosen accordingly.