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The frequency and nature of adverse events in acute Irish hospitals: the Irish National Adverse Events Study

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posted on 22.11.2019, 18:28 authored by Natasha Rafter

Irish healthcare has undergone extensive change with spending cuts and a focus on quality initiatives. However, little is known about adverse event occurrence. This thesis assesses the frequency and nature of adverse events in Irish hospitals and compares the results to international adverse events data, using a systematic review methodology and conducting the Irish National Adverse Events Study (INAES).

Retrospective patient chart review based on the Harvard Medical Practice Study methodology was undertaken. A random sample of adult in-patient admissions from 2009 was selected from eight hospitals, stratified by region and size, across the Republic of Ireland. 1,574 patient charts (53% female, mean age 54 years) underwent two-stage review (stage-one: nurse review for triggers; stage-two physician review of triggered charts for adverse events) with electronic data capture. Results were weighted to reflect the national case mix. The impact on adverse event rate of differing application of international adverse event criteria was also examined.

In stage-one 45% of charts were triggered. The prevalence rate (risk) of adverse events in admissions was 12.2% (95% CI 9.5% – 15.5%), with an incidence of 10.3 events per 100 admissions (95% CI 7.5 – 13.1). Over 70% of events were considered preventable. Two-thirds were rated as having a mild to moderate impact on the patient, 10% resulted in permanent impairment and 6.7% contributed to death. A mean of 6.1 added bed days was attributed to events, representing an additional expenditure of €5,550 per event.

This first study of adverse events in Ireland reported similar rates to other countries. In a time of austerity, adverse events in adult in-patients were estimated to cost approximately €200 million. These results provide important baseline data on the adverse event burden and, alongside web-based chart review, provide an incentive and methodology to monitor future patient safety initiatives


Health Research Board of Ireland (Research Collaborative in Quality and Patient Safety)


First Supervisor

Professor David Williams

Second Supervisor

Professor Anne Hickey


A thesis submitted for the degree of Doctor of Medicine from the Royal College of Surgeons in Ireland in 2016.

Published Citation

Rafter, NJ. The frequency and nature of adverse events in acute Irish hospitals: the Irish National Adverse Events Study [MD Thesis]. Dublin: Royal College of Surgeons in Ireland; 2016.

Degree Name

Doctor of Medicine (MD)

Date of award


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