Practical approach to determining costs and frequency of adverse drug events in a health care network.

The frequency, preventability, severity, root causes, and projected costs of adverse drug events (ADEs) occurring after or causing admission to a four-hospital integrated academic health network were studied. The sample included all admissions during a 53-day study period. Events were identified through daily record review of a random patient sample, computerized flags, and self-reporting. A case review committee validated the occurrence, classification, and root causes of the events. Additional length of stay and costs associated with ADEs were analyzed by using a case-control, multiple linear regression model. The estimated ADE rate during hospitalization was 4.2 events per 100 admissions, with a cost of $2162 per ADE. In addition, 3.2% of admissions were caused by ADEs, with an associated cost of $6685 per event. Fifteen percent of hospital ADEs and 76% of ADEs causing admission were judged preventable. The annual cost to the organization for events occurring during hospitalization was $1.7 million, and the cost of preventable ADEs was $260,000, while the projected costs of preventable ADEs causing admission were $3.8 million. The rate of admissions to the mental health center caused by ADEs was higher than for other settings at 13.6%, with a cost of preventable ADEs of $1.3 million. Patient noncompliance was judged to be the cause of the 69% of the ADEs causing admission. Seventy-one percent of the serious medication errors occurred at the prescribing stage of the medication-use process. ADEs were frequent, costly, and often preventable and resulted in many admissions to a mental health center.