Medical malpractice as an epidemiological problem.

The notion that the tort liability system deters negligence in health care has been invoked to make the "business case for patient safety." However, existing data on the relationship between hospital adverse events and malpractice claims typically are interpreted as evidence that the tort system does not deter negligence because of the poor fit between those who are negligently injured and those who sue. Using a familiar analogy from epidemiology--the problem of false positives in screening tests for rare diseases--and data from two large studies of medical injuries and malpractice claims in the United States, this paper presents an argument that the standard interpretation overlooks a complexity in the data. Although most malpractice claims do not actually involve a negligent injury, a patient who suffers a negligent injury is more than 20 times more likely, on average, to file a claim than a patient who does not. However, because malpractice claiming is a rare event with many false positives, for the average hospital or group practice, even substantial improvements in rates of negligent injury will not lead to a large reduction in claims rates. These findings suggest that the strength of the business case for patient safety depends on the perspective from which one views the data.