About 40% of medical malpractice cases filed in the United States are groundless, according to a Harvard researcher who previously conducted a separate study of just nursing home claims.

The findings challenge the view of tort-reform advocates that frivolous claims resulting in exorbitant payouts are rampant in the legal system, according to lead researcher, David Studdert of the Harvard School of Public Health. Many of the frivolous claims were dismissed without a payout or trial, he noted.

“We found the system did reasonably well in sorting the good claims from the bad ones, but there were problems,” Studdert said.

Many of the lawsuits examined, which were filed primarily over acute care issues, contained no evidence that a medical error was committed or the patient suffered injury, the study found. While most were dismissed without a payout, groundless suits still accounted for 15% of the money paid out in settlements or verdicts. Study findings appeared in the New England Journal of Medicine.

Studdert previously conducted a study of lawsuits against nursing homes that found an astronomically high percentage (around 90%) resulted in some sort of payout, usually in the form of a settlement.