• patient safety
• adverse events
• measurement methodology

The Harvard Medical Practice Study (HMPS)^1,2 was not the first study to examine adverse events in healthcare organizations, but it established the standard by which adverse events are measured and laid the groundwork for policy discussions on patient safety in several countries. This commentary examines the impact of the study on research and policy in the US and elsewhere.

The methods used in the HMPS were based on the 1977 California medical insurance feasibility study.³ The refining and rigorous application of these methods to a random sample of patients and hospitals offered one of the first large sample estimates of adverse events in the health services research literature.

Today the HMPS is best known for the methods developed to identify adverse events and estimate their incidence. Yet this was only one of the investigators’ goals. Defining the incidence of adverse events was necessary for evaluating whether the tort system was effective in rewarding those who are injured as a result of their care in hospitals and assessing the economic consequences of such injuries. The dramatic finding that adverse events were a common component of hospital care has largely overshadowed the attention given to the evaluation of the tort system and assessment of costs.

The HMPS method for identifying adverse …