The emergency department (ED) abounds with hazards that might lead to adverse events (AEs). Clinicians must make frequent, high-consequence decisions with high diagnostic uncertainty as part of ad hoc teams taking care of patients not generally known to them.1 This occurs in the context of a sometimes chaotic environment with frequent interruptions, handoffs and shift changes. As a result, the ED tends to magnify cognitive biases that can result in AEs—particularly diagnostic AEs.2 This is especially problematic for children who account for 23 million ED visits in the USA annually and are particularly vulnerable to AEs. Children are developmentally less able to communicate specific symptoms and are evaluated in EDs with variable readiness to care for them.3 Yet, little is known about the occurrence and nature of AEs in paediatric ED patients.

In this issue of BMJ Quality & Safety, Plint and colleagues4 sought to address this gap. They conducted a prospective observational study of children visiting nine Canadian paediatric EDs to determine whether an AE occurred within 3 weeks of a visit.5 AEs were defined as ‘any event resulting in unintended patient harm that was related to the care provided rather than to an underlying medical condition’. They found that 3% of visits were associated with an AE, of which 77% were judged to be preventable. The most common AEs related to management, diagnosis and medication. Although the large majority of AEs were minor, half prompted the need for subsequent care. Risk factors associated with a preventable AE were increasing age, history of chronic condition, increasing time to initial ED assessment and evaluation in the acute care area (rather than the ambulatory area).

This study illuminates an underexplored area in paediatric emergency care: given its inherent hazards, how often do AEs happen? Plint and colleagues improved on their prior single-centre study,6 providing more precise and stable estimates of AE rates in this population while bolstering external validity, since estimates were consistent across the nine centres. Given that most AEs were preventable, this study also provides a clear basis for robust quality improvement efforts that have potential to reduce such AEs.

The key strengths of this study are its multicentre nature with high enrolment numbers, and impressive and meticulous efforts to follow patients forward from their ED visit, resulting in a robust identification of AEs. Investigators selected an unbiased sample of ED shifts, examined associated hospital records of admitted patients using the Canadian Paediatric Trigger Tool and made every effort to contact all patients to identify AEs. While it would be impossible to avoid recall bias when interviewing families about their past experiences, investigators minimised this risk through a multipronged, preplanned strategy of AE identification and vetting. This study’s findings therefore represent an important advance in our understanding of AEs occurring in paediatric emergency care.

As in any study, there were a number of limitations, including some that are common to most studies of AEs. Although the data are from 2014 to 2015, this is unlikely to affect the types of AEs detected or diminish the study’s significance. The types of conditions seen and potential events that occurred in the ED (such as peripheral intravenous catheter infiltrations, bleeding events, delayed diagnoses) are unlikely to have significantly changed since these data were collected. The main limitations involve three key issues: (1) methodological approaches affecting AE rates, (2) inherent subjectivity in AE determination, and (3) generalisability of paediatric ED AE rates to all EDs where children receive care.