The incidence of adverse events in Swedish hospitals: a retrospective medical record review study

OBJECTIVES: To estimate the incidence, nature and consequences of adverse events and preventable adverse events in Swedish hospitals. DESIGN: A three-stage structured retrospective medical record review based on the use of 18 screening criteria. SETTING: Twenty-eight Swedish hospitals. Population A representative sample (n = 1967) of the 1.2 million Swedish hospital admissions between October 2003 and September 2004. MAIN OUTCOME MEASURES: Proportion of admissions with adverse events, the proportion of preventable adverse events and the types and consequences of adverse events. RESULTS: In total, 12.3% (n = 241) of the 1967 admissions had adverse events (95% CI, 10.8-13.7), of which 70% (n = 169) were preventable. Fifty-five percent of the preventable events led to impairment or disability, which was resolved during the admission or within 1 month from discharge, another 33% were resolved within 1 year, 9% of the preventable events led to permanent disability and 3% of the adverse events contributed to patient death. Preventable adverse events led to a mean increased length of stay of 6 days. Ten of the 18 screening criteria were sufficient to detect 90% of the preventable adverse events. When extrapolated to the 1.2 million annual admissions, the results correspond to 105,000 preventable adverse events (95% CI, 90,000-120,000) and 630,000 days of hospitalization (95% CI, 430,000-830,000). CONCLUSIONS: This study confirms that preventable adverse events were common, and that they caused extensive human suffering and consumed a significant amount of the available hospital resources.