The HMPS I: Adverse events in patients and negligence [Classics Series]

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1. It was found that adverse events occurred in 3.7% of hospitalizations.

2. Approximately 27.6% of adverse events occurring in hospital were attributed to negligence.

Study Rundown: This study identified a significant burden from iatrogenic injury with a substantial proportion of adverse events in hospital leading to permanent disability or death. Of note was the significant number of adverse events resulting from substandard care, which may be reduced by quality assurance measures. Increasing age was identified as an important risk factor for the occurrence of adverse events, likely reflecting more complicated illness and poorer health. Limitations of the study include the difficulty of evaluating negligence and degree of disability from hospital records; however, the validity and reliability of the review process were tested and found to be reasonably high with 89% sensitivity in screening for adverse events and 89% agreement on the presence of an adverse event. Other strengths of the study were the large sample size and the use of a random sample which allowed extrapolation to population estimates.

In sum, the HMPS I was one of the earliest and largest efforts to quantify the incidence of adverse events and their impacts. It also determined that many adverse events were potentially preventable, and these findings justified greater investment in quality improvement initiatives.

Please click to read study in NEJM

In Depth [retrospective, case review]: The purpose of the Harvard Medical Practice Study (HMPS) I, published in NEJM in 1991, was to produce a reliable estimate of the incidence of adverse events and negligence in hospitalized patients. The results are based on the review of 30,121 records from a random sample of 2,671,863 non-psychiatric patients in New York in 1984. Records were first screened by nurses and medical record analysts. Those identified as positive for the occurrence of an adverse event were independently reviewed by two physicians. Physicians identified 1,278 adverse events, of which 306 were due to negligence. From this, the statewide incidence rate of adverse events was estimated to be 3.7%, while approximately 27.6% of these events were the result of negligence. The majority of adverse events led to disability that resolved in less than six months; however, 2.6% led to permanent total disability and 13.6% resulted in death. Rates of adverse events were positively correlated with increasing age (P<0.0001) and negligence was more frequently implicated with increasing severity of adverse events, causing 22% of events leading to temporary disability and 51% of events resulting in death (P<0.0001). The percentage of adverse events due to negligence did not vary between clinical specialties.

By Adrienne Cheung, Andrew Cheung, M.D.

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