Although the national focus has been on patient safety for more than a decade, medical errors and other adverse events occur in one-third of hospital admissions—a rate as much as 10 times higher than some estimates had indicated, according to a study in the April issue of Health Affairs.

David C. Classen, MD, MS, associate professor of medicine at the University of Utah in Salt Lake City, and colleagues from the Institute for Healthcare Improvement (IHI) conducted a patient safety study evaluating the incidence of adverse events for inpatients at three hospitals including a retrospective record review using IHI's Global Trigger Tool, each hospital’s voluntary sentinel event or other incident or event reporting system and screening with the Agency for Healthcare Research and Quality (AHRQ) Patient Safety Indicators.

Among the 795 patient records reviewed, 393 adverse events were detected by all three methods combined. The Global Trigger Tool methodology detected 354 adverse events (90.1 percent of the total), the local hospital reporting systems detected 4 adverse events (1 percent), and the Patient Safety Indicators detected 35 adverse events (8.99 percent).

Overall, adverse events occurred in 33.2 percent of hospital admissions (range: 29–36 percent) or 91 events per 1,000 patient days (range: 89–106). Some patients experienced more than one adverse event; the overall rate was 49 events per 100 admissions (range: 43–56). Patients who experienced adverse events were older and had higher mortality, greater hospital length of stay and a higher case mix index (a measure of the characteristics of patients treated based on resource use and intensity of care) than patients without an adverse event, Classen and colleagues stated.

The AHRQ indicators and voluntary reporting missed more than 90 percent of adverse events identified by the Global Trigger Tool, the researchers reported. “If anything, our findings are conservative, because they rely on medical record review, which would not detect as many adverse events as direct, real-time observation would,” the authors remarked.

Although the Global Trigger Tool is a more resource-intensive method because it involves medical record review, the researchers suggested that it could be incorporated into commercial EHR systems, thus making it easier and less costly to use.

“Reliance on voluntary reporting and the Patient Safety Indicators could produce misleading conclusions about the current safety of care in the U.S. healthcare system and misdirect efforts to improve patient safety,” the researchers concluded.