Analyzing data from the Utah and Colorado Medical Practice Study, investigators reviewed nearly 15,000 hospital discharge records and discovered 587 adverse events, 31 of which were ambulatory care preventable adverse events (APAEs). The most common type of APAE was a missed or delayed diagnosis, a concern also found in a past study of closed malpractice claims. Extrapolated to the national population, the authors estimate that 75,000 hospitalizations annually are due to preventable adverse events in the ambulatory setting, with 10% resulting in permanent injuries or death.