A medical error is a preventable adverse effect of care, whether or not it is evident or harmful to the patient. This might include an inaccurate or incomplete diagnosis or treatment of a disease, injury, syndrome, behavior, infection, or other ailment. Globally, it is estimated that 142,000 people died in 2013 from adverse effects of medical treatment; this is an increase from 94,000 in 1990. However, a 2016 study of the number of deaths that were a result of medical error in the U.S. placed the yearly death rate in the U.S. alone at 251,454 deaths, which suggests that the 2013 global estimation may not be accurate.
A WHO 1993 survey of 34 laboratories worldwide that were supposed to give early warning of epidemic disease revealed that only half the laboratories could diagnose yellow fever reliably, 56% couldn't identify hantaviruses, 82% didn't diagnose California encephalitis, and most laboratories were not equipped at all to test for rarer viral infections, such as Ebola, Lassa and Machupo.
The diagnosis of pulmonary embolism (PE) is missed more than 400,000 times in the USA each year, and approximately 100,000 patients die who would have survived with the proper diagnosis and treatment. It is especially likely to be missed in older patients. The correct diagnosis of PE is made in 30% of all patients who die with massive PE but in only 10% of those who are 70 years of age or older. It is the most commonly missed diagnosis responsible for death in the elderly institutionalized patient. Untreated, approximately one-third of patients who survive an initial pulmonary embolism will die from a future embolic episode.