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System errors, not patient factors, are responsible for most hospital medication errors

Over 6 of every 100 patients admitted to the hospital suffer a drug-related injury (adverse drug event or ADE). In a recent study, sicker patients with longer hospital stays were more likely than other patients to experience problems from medications. Patient-level risk factors had a smaller than expected impact, according to the study by the ADE Prevention Study Group. The group, supported in part by the Agency for Healthcare Research and Quality (HS07107), found that after controlling for level of care and pre-ADE length of hospital stay, only a few patient factors (for example, age, multiple drug therapy, and impaired renal or liver function) increased the risk of suffering from an ADE. What's more, the group of patients with such risk factors was relatively small.

This suggests that improving systems by which hospital drugs are ordered, dispensed, and administered rather than targeting ADE-prone individuals is more apt to succeed in battling this important and costly problem, according to David W. Bates, M.D., M.Sc., of Brigham and Women's Hospital. System approaches often involve the use of patient-specific data. For example, data indicating a patient has renal failure will prompt physicians to adjust aminoglycoside dosages. Other system approaches might include development of standardized labeling for tubing in situations in which multiple intravenous medications are being administered simultaneously.

The study group based their findings on analysis of patient factors associated with ADEs for 4,108 patients admitted to two hospitals. They used computerized data from one hospital and case patients with an ADE and matched control patients from another hospital. The drug exposure data in the case-control analysis suggested that no major drug class was responsible for a disproportionate share of the ADEs, with the possible exception of analgesics.

See "Patient risk factors for adverse drug events in hospitalized patients," by Dr. Bates, Elizabeth B. Miller, David J. Cullen, M.D., M.Sc., and others, in the November 22, 1999, Archives of Internal Medicine 159, pp. 2553-2560.

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