The Institute of Medicine Report on Medical Errors: Misunderstanding Can Do Harm

Quality of Health Care in America Committee*

In This Article

Harm From Medical Errors Is Great

The IOM Committee concluded that tens of thousands of Americans die each year as a result of medical errors, and that even larger numbers suffer temporary or permanent harm. The conclusion of the IOM Committee was based on the results of over 30 publications in leading peer review journals over the last 10-12 years, not on 1 or 2 studies as is sometimes asserted.[4]

The IOM figures regarding injuries and deaths are estimates, but they are reasonable estimates. It is important to understand how they were obtained. The higher estimate, that nationwide 98,000 people die annually as the result of errors in medical management, is a 1998 extrapolation from the findings of the medical record review study conducted using 1984 data and released by the Harvard Medical Practice Study (MPS) in 1991.[5] The lower figure of 44,000 is based on a study conducted in Colorado and Utah hospitals about 8 years later.[6] In a recent Sounding board piece, it was asserted that "neither study ...involved judgments by the physicians reviewing medical records about whether the injuries were caused by errors."[4] This is not so.

The MPS study found that 3.7% of patients hospitalized in New York State in 1984 suffered an adverse event (AE), defined as a disabling injury caused by treatment, and that 13.6% of these patients died as a result of the AE. Physician reviewers did, in fact, make judgments as to the presence of an error. In the same issue of The New England Journal of Medicine that reported these results is the companion paper from the MPS, The Nature of Adverse Events,[7] which states: "In addition, the reviewers were asked to indicate whether each adverse event could have been caused by a reasonably avoidable error, defined as a mistake in performance or thought." Of all AEs identified, 58% were judged by 2 physician reviewers to be due to an error. This is the figure IOM used. The study conducted in Colorado and Utah in 1992 used methods similar to the MPS (except that only 1 physician review was used).[6]

Unfortunately, the IOM numbers, shocking as they are, probably underestimate the extent of preventable medical injury, for 2 important reasons. First, they are based on data extracted from medical records. Many injuries, and most errors, are not recorded in the medical record, either by intent or by inattention, or, more likely, because they are not recognized.[8,9,10]

The second reason the IOM estimates are probably low is that they exclude outpatient injuries. We know very little about the extent of AEs in ambulatory care, but there is no evidence the error rate is less. In fact, absent hospital safeguards, regulation, and peer supervision it might well be higher. A recent study reported that 10% of office prescriptions had significant errors.[11] Recent reports of deaths of inpatients undergoing a supposedly routine procedure, liposuction, are not reassuring.[12] None of these injuries or deaths are included in the IOM estimates. In 1996, 31.5 million ambulatory surgeries and procedures were performed.[13] Even if only one half of 1% of these patients experienced a preventable AE (one fifth the inpatient rate), that alone would impact over 100,000 individuals.

The limitations of population-based studies become evident when in-depth studies "drill down" into specific clinical areas. Almost invariably, error and injury rates are found to be much higher. DuBois found that 20% (14% to 27%) of deaths from acute myocardial infarction, pneumonia, or cerebrovascular accident were preventable.[14] Bedell reported that 64% of in-hospital cardiac arrests were preventable.[15] Andrews found that 17% of ICU patients had preventable serious or fatal AE.[16] Autopsy studies have repeatedly shown fatal diagnostic error rates of 20% to 40%.[17,18,19,20,21] The Centers for Disease Control and Prevention (CDC) estimates that 2.7% of surgical operations are complicated by surgical-site infections, accounting for nearly 500,000 nosocomial infections each year.[22] One large controlled study found the excess mortality rate of surgical-site infections to be 4.3%, suggesting 20,000 deaths annually from this cause alone.[23]

Some maintain that the change from 98,000 in 1984 to 44,000 in 1992 indicates that patient safety has improved.[4] This is not justified. The studies differed enough with regard to site and methodology to make comparisons inappropriate.

Furthermore, the continuing pace of innovation makes it unlikely that total number of injuries due to errors has significantly declined. The last 15 years has witnessed an unprecedented acceleration in the creation and implementation of new technologies. Each one carries both benefits and new opportunities for error. Recall the many reports of complications attributed to the "learning curve" of laparoscopic cholecystectomy,[24] which still is associated with a higher complication rate than the open procedure.[25] In addition, hundreds of new drugs have been introduced during this period. Many are more effective than the ones they replaced, but this potency increases the risk of severe injuries when they are misused, and the increasing variety of medications leads to more opportunities for confusion.