The nature of adverse events in hospitalized patients. Results of the Harvard Medical Practice Study II.
BACKGROUND
In a sample of 30,195 randomly selected hospital records, we identified 1133 patients (3.7 percent) with disabling injuries caused by medical treatment. We report here an analysis of these adverse events and their relation to error, negligence, and disability.


METHODS
Two physician-reviewers independently identified the adverse events and evaluated them with respect to negligence, errors in management, and extent of disability. One of the authors classified each event according to type of injury. We tested the significance of differences in rates of negligence and disability among categories with at least 30 adverse events.


RESULTS
Drug complications were the most common type of adverse event (19 percent), followed by wound infections (14 percent) and technical complications (13 percent). Nearly half the adverse events (48 percent) were associated with an operation. Adverse events during surgery were less likely to be caused by negligence (17 percent) than nonsurgical ones (37 percent). The proportion of adverse events due to negligence was highest for diagnostic mishaps (75 percent), noninvasive therapeutic mishaps ("errors of omission") (77 percent), and events occurring in the emergency room (70 percent). Errors in management were identified for 58 percent of the adverse events, among which nearly half were attributed to negligence.


CONCLUSIONS
Although the prevention of many adverse events must await improvements in medical knowledge, the high proportion that are due to management errors suggests that many others are potentially preventable now. Reducing the incidence of these events will require identifying their causes and developing methods to prevent error or reduce its effects.
Leape
L L
LL
Department of Health Policy and Management, Harvard School of Public Health, Boston, MA 02115.
Brennan
T A
TA
Laird
N
N
Lawthers
A G
AG
Localio
A R
AR
Barnes
B A
BA
Hebert
L
L
Newhouse
J P
JP
Weiler
P C
PC
Hiatt
H
H
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D003951:Diagnostic Errors; D006233:Persons with Disabilities; D064420:Drug-Related Side Effects and Adverse Reactions; D006753:Hospital Records; D006761:Hospitals / Q000592:standards / Q000706:statistics & numerical data*; D006801:Humans; D007049:Iatrogenic Disease / Q000453:epidemiology*; D007297:Inpatients / Q000706:statistics & numerical data*; D008318:Malpractice / Q000706:statistics & numerical data*; D008875:Middle Aged; D009017:Morbidity; D009518:New York / Q000453:epidemiology; D011897:Random Allocation; D012307:Risk Factors; D012494:Sampling Studies; D014946:Wound Infection / Q000453:epidemiology