A report this week in Health Affairs finds that adverse events occur in 33.2 percent of hospital admissions, or 91 events per 1,000 patient days. Those rates are considerably higher than previously suspected, the authors argue.

The researchers, funded by the Robert Wood Johnson Foundation, used the Institute for Healthcare Improvement's Global Trigger Tool as a guideline for discovering adverse events. According to the report, traditional event detection methods, including AHRQ's Patient Safety Indicators and voluntary reporting, may miss up to 90 percent of adverse events.

In a statement, AHA President and CEO Rich Umbdenstock said hospitals are dedicated to improving patient quality and safety to prevent adverse events. "Hospitals are actively engaged in quality improvement efforts and are eager to identify and use strategies and tools that can further improve patient safety," he said.

On average, patients experiencing adverse events were older, had greater hospital length of stay and a higher case-mix index than the norm, the study also found. Read the full report here.