TABLE C-5 Hospital Care: ADE Incidence During Hospitalization


ADEs per 100 Admissions

ADEs per 1,000 Patient-Days

Proportion of ADEs Preventable

Classen et al., 1997


Not given

About 50 percent (out of 2,227 ADEs in study)

Senst et al., 2001


Not given

15 percent (out of 74 ADEs in the study

Bates et al., 1995b



28 percent (out of 247 ADEs in study)

Jha et al., 1998

Not given


27 percent (out of 617 ADEs in study)

Nebeker et al., 2005



27 percent (out of 483 ADEs in study)

ing these figures nationally and assuming 32 million admissions annually, the authors concluded that 770,000 hospital patients in America would experience an ADE annually.

Another study, conducted at two tertiary care hospitals in Boston, involved 4,031 adult admissions. Carried out in 1993 under the Adverse Drug Events Prevention Study, this study found an overall ADE rate of 6.5 per 100 nonobstetric admissions (or 11.5 ADEs per 1,000 patient-days); of these, 28 percent were judged preventable (Bates et al., 1995b). Of the ADEs, 1 percent were fatal (none preventable), 12 percent life-threatening, 30 percent serious, and 57 percent significant. Of the life-threatening and serious ADEs, 42 percent were judged preventable. Assuming an ADE rate of 6.5 per 100 nonobstetric admissions and 25 million nonobstetric admissions to short-term hospitals annually, the authors estimated an annual rate of 1.6 million ADEs in U.S. hospitals.

A third study, utilizing data on ADEs collected in the summer of 1998 from a four-hospital academic medical network, estimated the ADE rate during hospitalization to be 4.2 per 100 admissions (Senst et al., 2001). Fifteen percent of these ADEs were judged preventable.

At a tertiary hospital in Boston, in a study carried out from October 1994 to May 1995, 617 ADEs were observed, 166 of which were judged preventable (Jha et al., 1998). After adjustment for the sampling scheme, the ADE rate was estimated to be 21 per 1,000 patient-days.

Much higher ADE rates were observed in the most recent study, involving a highly computerized hospital that had implemented electronic health records (Nebeker et al., 2005). Computerized order checking was fully functional for allergies, many drug–drug interactions, and limited drug– disease interactions. The system did not, however, feature sophisticated decision-support algorithms. Among 937 hospital admissions, 483 clinically significant inpatients ADEs were identified—52 per 100 admissions,

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