THURSDAY, April 7 (HealthDay News) -- A new method for identifying medical errors contends that as many as 90 percent of hospital mistakes are overlooked.

The actual error rate is 10 times greater than previously thought, despite a recent focus on reducing error rates and improving patient safety, a new study suggests.

"The more you look for errors, the more you find," said lead researcher Dr. David C. Classen, an associate professor of medicine at the University of Utah.

"There is a large opportunity for improvement, despite all the work that's been done," he said. "And we need better measurement systems to assess how we are doing in patient safety."

One factor in the high number of errors is that hospital patients tend to be sicker than they were years ago, Classen noted. With the advent of outpatient treatment, "the healthier patients are no longer in hospitals," he said.

"We have a much more complicated patient mix, more problems, more medications, so there is more room for error," Classen explained.

In addition, better methods exist for detecting errors, he said. In this study, researchers used a new comprehensive review of hospital records, called the Global Trigger Tool. Moreover, the tool was used by experienced reviewers from outside the hospitals, Classen said.

Most hospitals rely on voluntary error reporting systems or coding systems that utilize records on patients' charts, Classen said. These are the methods recommended by the U.S. Agency for Healthcare Research and Quality (AHRQ), he noted.

"It turns out that both those methods are dramatically inferior to Global Trigger Tool," Classen said. "The problem is that most hospitals use these methods to track their safety problems, and they are missing 90 percent of them," he stated.

The report is published in the April issue of Health Affairs.

For the study, Classen's team compared the Global Trigger Tool with the methods recommended by the AHRQ.

Applying both tools to 795 patient records, the researchers found the AHRQ methods identified 35 errors, while the Global Trigger Tool found 354 errors.

Medication errors were most common, followed by errors in surgical and nonsurgical procedures and in common infections, Classen said.

"These are the areas where we have always found problems," he said. "Obviously, we still have a lot of room for improvement."

These findings are conservative, the researchers pointed out, because the error rate is based on a review of medical records, which cannot identify as many errors as direct, real-time observation.

Classen noted that any hospital can use the Global Trigger Tool. "A number of people believe a tool like this should become a standard measure of safety in U.S. hospitals," he said.

The Global Trigger Tool takes more time and resources than other methods, the researchers said. However, it could become part of electronic medical record systems, which would integrate it easily into the hospital, they noted.

Commenting on the study, Dr. John Birkmeyer, director of the Center for Healthcare Outcomes and Policy at the University of Michigan, said that "in some respect their finding isn't surprising."

"Nobody is surprised that systems that rely on voluntary reporting would tend to let a high percentage of cases fall through the cracks," he said. "It's not a surprise that a method based on careful chart abstraction by knowledgeable reviewers would do a much better job in tracking adverse events."

One problem, Birkmeyer noted, is that a system like the Global Trigger Tool can be too sensitive and may pick up unimportant things.

"The tool that the researchers describe here is a significant step forward," Birkmeyer said. "The problem is that this method may suffer by being a little bit too sensitive and throwing into one bucket too many things," he warned.

Birkmeyer noted that most of the errors the researchers identified were the least severe. "This is probably not the best tool for giving patients information about the quality of a hospital," he said.

Systems need to both capture all the information on medical errors, and also rank the data to take into account the actual consequence to patient health, Birkmeyer said.

More information

For more information on patient safety, visit the U.S. National Library of Medicine.