Nearly one-in-five Medicare patients are victims of medical injuries that often aren’t related to their underlying disease or condition, according to new research.

The injuries included: being given the wrong medication, having an allergic reaction to a medication, or receiving any treatment that led to more complications of an existing medical problem. About two-thirds of these injuries occurred during outpatient care, rather than in the hospital, the study findings showed.

“These injuries are caused by the medical care or management rather than any underlying disease,” said lead researcher Mary Carter, director of the Gerontology Program at Towson University in Maryland.

For the study, Carter and her colleagues collected data on more than 12,500 Medicare patients who made claims between 1998 and 2005. Their average age was 76.

The researchers found that 19% of those included in the study experienced at least one adverse medical event. That’s higher than previous research estimates that suggested the rate of adverse medical events was probably around 13.5% for hospitalized patients, according to background information in the study.

While there has been a great deal of effort in trying to understand medical injury in hospitals, not as much has been done in clinics, doctor’s offices, outpatient surgery centers, emergency rooms and nursing homes, noted Carter. “To really improve our ability to prevent these types of adverse events, we have to focus at least as much on outpatient care as we do on inpatient care,” Carter said.