A new study by patient safety experts estimates that each year, as many as 40,500 critically ill U.S. hospital patients die with an unknown medical condition that could have caused or contributed to their death.
In the study, conducted by the Johns Hopkins University School of Medicine and published online in the journal BMJ Quality & Safety, researchers say that diagnostic errors in the intensive care unit may claim as many lives each year as breast cancer but remain a relatively unperceived cause of preventable patient harm.
"Our study shows that misdiagnosis is alarmingly common in the acute care setting,” said lead author Dr. Bradford Winters in a statement. Winters is an associate professor of anesthesiology and critical care medicine and neurology and surgery in the Johns Hopkins University School of Medicine. “To date, there’s been very little research to determine root causes or effective interventions,” Winters said.
Researchers at the Johns Hopkins Armstrong Institute for Patient Safety and Quality reviewed 31 studies that included 5,863 autopsies to detect diagnostic errors in adult ICU patients. Their review found that 28 percent of patients — more than one in four — had at least one missed diagnosis at death.
In 8 percent of patients, the diagnostic error was serious enough that it may either have caused or directly contributed to the individual’s death and, if known, likely would have changed treatment, according to the study. Infections and vascular conditions, such as heart attack and stroke, accounted for more than three-quarters of those fatal flaws.
The prevalence of autopsy-detected misdiagnoses, which were stratified by severity, ranged from 5.5 to 100 percent by study.
Overall, the medical conditions most commonly missed by diagnosticians included heart attack; pulmonary embolism, an artery blockage in the lungs; pneumonia; and aspergillosis, a fungal infection that most commonly affects individuals with a weakened immune system. Cumulatively, these four conditions accounted for about one-third of all illnesses that doctors failed to detect.
Misdiagnoses were classified based on four categories: vascular, which included conditions involving vessel blockages and bleeding, such as heart attack and stroke; all bacterial, viral and fungal infections; mechanical pathophysiological, a broad range of organ malfunction such as congestive heart failure and bowel obstruction; and cancer.
The study also found that when compared with adult hospital patients overall, individuals in the ICU face up to a twofold risk of suffering a potentially fatal diagnostic mistake.
“It may be counterintuitive to think that the patients who are the most closely monitored and frequently tested are more commonly misdiagnosed, but the ICU is a very complex environment,” Winters said. Clinicians often face an overflow of information in a distracting environment in which the sickest patients compete for attention, most without being able to communicate with their medical team. “We need to develop better cognitive tools that can take into account the 7,000 or more pieces of information that critical care physicians are bombarded with each day to ensure we’re not ruling out potential diagnoses,” he said.
After collecting and classifying all error data, the researchers calculated how frequently misdiagnoses would be discovered if every patient who died in the ICU underwent an autopsy. Although autopsy is more frequently performed in complex patient cases in which the clinician may have a lower level of diagnostic certainty, the authors say their calculations are conservative estimates.
Although two-thirds of discovered misdiagnoses did not directly contribute to the patient’s death, they are an important indicator of accuracy and are not without costs, according to the study. Patients may have to endure longer hospital stays, unnecessary surgical procedures and reduced quality of life because of non-fatal diagnostic mistakes.