Prehospital Triage of Acute Aortic Syndrome Using a Machine Learning Algorithm

Background: Acute aortic syndrome (AAS) comprises a complex and potentially fatal group of conditions requiring emergency specialist management. The aim of this study was to build a prediction algorithm to assist prehospital triage of AAS. Methods: Details of consecutive patients enrolled in a regional specialist aortic network were collected prospectively. Two prediction algorithms for AAS based on logistic regression and an ensemble machine learning method called SuperLearner (SL) were developed. Undertriage was defined as the proportion of patients with AAS not transported to the specialist aortic centre, and overtriage as the proportion of patients with alternative diagnoses but transported to the specialist aortic centre. Results: Data for 976 hospital admissions between February 2010 and June 2017 were included; 609 (62.4 per cent) had AAS. Overtriage and undertriage rates were 52.3 and 16.1 per cent respectively. The population was divided into a training cohort (743 patients) and a validation cohort (233). The area under the receiver operating characteristic (ROC) curve values for the logistic regression score and the SL were 0.68 (95 per cent c.i. 0.64 to 0.72) and 0.87 (0.84 to 0.89) respectively (P < 0.001) in the training cohort, and 0.67 (0.60 to 0.74) and 0.73 (0.66 to 0.79) in the validation cohort (P = 0.038). The logistic regression score was associated with undertriage and overtriage rates of 33.7 (bootstrapped 95 per cent c.i. 29.3 to 38.3) and 7.2 (4.8 to 9.8) per cent respectively, whereas the SL yielded undertriage and overtriage rates of 1.0 (0.3 to 2.0) and 30.2 (25.8 to 34.8) per cent respectively. Conclusion: A machine learning prediction model performed well in discriminating AAS and could be clinically useful in prehospital triage of patients with suspected AAS.