The vast majority of in-hospital adverse events go unreported by staff, according to a report from HHS' inspector general's office (PDF).

Using a month of survey data from a sample of 189 hospitals, the inspector general's office found that hospitals' voluntary incident reporting systems captured only about 14% of events that cause patient harm, such as medication errors. Federal investigators attributed low reporting rates, at least in part, to poor knowledge among hospital staff about what patient harm actually means.

“For example, staff reported only one of 17 sample events related to catheter usage (e.g., infection and urinary retention), a common cause of harm to Medicare beneficiaries,” according to the report.

Other types of events that went unreported included cases of excessive bleeding related to misuse of blood thinning medications, and hospital-acquired infections.

Incident reporting systems are a requirement for participation in Medicare, but a lack of uniform requirements—such as lists staff can use to identify patient harms—can damage the systems’ reliability, according to the report.

“Because hospitals rely on incident reporting systems to track and analyze events, improving the usefulness of these systems is critical to hospitals' efforts to improve patient safety,” the report said.

The report urged the CMS and HHS’ Agency for Healthcare Research and Quality to develop a list of adverse events for hospitals to use. Additionally, the office said, the CMS should reassess its methods for judging hospital compliance with the reporting-system requirement.