Background Adverse event(AE) detection in healthcare has traditionally relied upon several methods including: patient care documentation review, mortality and morbidity review, voluntary reporting, direct observation and complaint systems. A novel sampling strategy, known as the trigger tool (TT) methodology, has been shown to provide a more robust and valid method of detection. The aim of this research was to develop and assess a TT specific to ground-based Emergency Medical Services, to identify cases with the potential risk for adverse events and harm.

Methods The study was conducted between March and December 2015. A literature review identified 57 potential triggers, which were grouped together by experts using an affinity process. Triggers for other areas of potential AE/harm were additionally considered for inclusion. An interim TT consisting of nine triggers underwent five iterative rounds of derivation tests of 20 random patient care records (n=100) in two emergency medical services. A final eight-item trigger list underwent a large sample (n=9836) assessment of test characteristics.

Results The final eight-item TT consisted of triggers divided amongst four categories: Clinical, Medication, Procedural and Return-Call. The TT demonstrated an AE identification rate of 41.5% (sensitivity 79.8% (95% CI, 69.9% to 87.6%); specificity 58.5% (95% CI, 52% to 64.8%)). When identifying potential risk for harm, the TT demonstrated a harm identification rate of 19.3% (sensitivity 97.1% (95% CI, 84.7% to 99.9%); specificity 53.5% (95% CI, 47.7% to 59.3%)).

Discussion The Emergency Medical Services Trigger Tool (EMSTT) may be used as a sampling strategy similar to the Global Trigger Tool, to identify and measure AE and harm over time, and monitor the success of improvement initiatives within the Emergency Medical Services setting.