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August 01 2001
VitalSTATS
How many people really die as a result of medical errors?
Regular readers of VitalSTATS may remember the outcry when an Institute of Medicine (IOM) report in 1999 estimated that as many as 98,000 Americans die each year as a result of medical errors. But now a new study in the Journal of the American Medical Association (JAMA) says that there may be as few as 5,000 such deaths annually. The press generally rose to the occasion and presented arguments from authors of both reports (e.g. "Study revisits medical error deaths, Number of mistakes may be overestimated, researchers suggest," Boston Globe, Jul. 25). But few of the reports sought to evaluate their relative strengths. Is the new study useful? What is the true position with regard to medical errors?
The IOM's estimates that between 44,000 and 98,000 hospital patients die each year because of medical mistakes (more than breast cancer, AIDS or highway accidents) were little more than "guesstimates," derived from hospital discharge data from a study in New York and from one in Colorado and Utah. There were several problems with the figures: It is not clear the three states concerned were representative of the country as a whole, and the classification of a doctor error was very broad (if a patient didn't tell the doctor about a medication which then caused complications, that was classified as a doctor error). Also, the studies were observational in nature and not designed to investigate causal relationships between errors and deaths. But perhaps the best indicator of the problems with the IOM figures is that, at the upper level, they would mean that 3 out of every 4 hospital doctors see one patient a year die as a result of medical error.
There are more than enough question marks over the IOM figures to make the new JAMA figures, from a study by Dr. Rodney A. Hayward, attractive. But they have their own problems.
Dr. Hayward reviewed cases of deaths involving medical errors in order to determine whether optimal medical care could have prevented an inevitable death. The study estimated that, under conditions of optimal care, only 6 percent of the patients subjected to medical errors would have left the hospital alive and only 0.5 percent would have lived three months or more "in good cognitive health." Hence, the estimate of only 5,000-15,000 deaths.
But the study utilized medical records from Veterans Affairs hospitals, whereas community hospitals would have been more representative of the medical profession as a whole. Additionally, Dr. Lucian L. Leape, one of the authors of the IOM study, criticized Dr. Hayward for using very small samples. He also accused the study of "statistical torturing" to obtain its results. While it is true that the study involved a lot of statistical manipulation, however, all the methods employed are statistically sound and commonly used in assessing risk.
Dr. Leape also told the Globe that he found the presumption that a medical error did not count if the patient would have died anyway "offensive. ... That is very much like a physician saying, 'Mrs Jones, I'm sorry I killed your husband with 10 times the dose of chemotherapy, but he would have died anyway.'" But the issue is much more complicated. If an elderly person near death catches a chest infection and dies, is it the chest infection or old age that has killed him or her? If Dr. Hayward's work is any guide, the same question often arises in the case of medical errors. This is one area where the idea of Quality Adjusted Life Years, a World Health Organization concept used to assess the economic "value" of a disease-ridden old age, might prove useful.
In addition, the IOM and JAMA studies have some flaws in common, since the measurement of medical error is as uncertain as the counting. Modern medicine is a complex affair. Although evidence of error is sometimes obvious, associations can be indirect, difficult to make, and open to debate. The assessment of blame appears too subjective to allow an accurate calculation of total cases. Indeed, Dr. Hayward discovered in his JAMA study that doctors rarely agree on whether or not an error led to a patient's death.
All in all, you've got to wonder about the validity of studies whose margins of error are more than 100 percent. Indeed, if we simply followed the numbers over time in the different studies, it would appear that medical error incidence has massively decreased. But the truth is we just don't know.
Nevertheless, Dr. Hayward believes the attention paid to the IOM study has been beneficial and has improved the quality of medical care. At the same time, he worries that such attention can become sensationalist and eventually scare off those who most need medical treatment. There is definitely a problem with medical errors, but we do not yet know enough about its scale to decide what we need to do about it. An informed public debate about the issue is a good thing, but simply throwing out scary numbers and calling for action is not. Until we have better numbers, policy makers run the risk of committing malpractice themselves.
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