• Accreditation
• Anaesthesia
• Attitudes

One important reason for the widespread attention given to the 1999 US Institute of Medicine (IOM) report To Err Is Human1 lie in its estimate that medical error was to blame for 44 000–98 000 deaths each year in the US hospitals. This striking claim established patient safety as a public concern, strengthened the case for improving the science underlying safety and motivated providers, policymakers, payers and regulators to take safety seriously. Some did express disquiet about the validity of the figures cited,2 including one of the principal investigators of the two studies that provided the data for these estimates.3

A decade and a half later, Makary and Daniel4 attribute an even higher toll to medical error: 251 454 deaths in US hospitals per year, making, they say, medical error the third-leading cause of death in the USA. Unsurprisingly, this claim generated widespread coverage in multiple media channels. It also ignited scientific controversy about the basis of the estimate and the role of mortality as a patient safety indicator (PSI). In this paper, we address this controversy and why it matters. We propose that the new estimate is very likely to be wrong. Not only is it wrong, it risks undermining rather than strengthening the cause of patient safety.