Dc. Classen et al., ADVERSE DRUG EVENTS IN HOSPITALIZED-PATIENTS - EXCESS LENGTH OF STAY,EXTRA COSTS, AND ATTRIBUTABLE MORTALITY, JAMA, the journal of the American Medical Association, 277(4), 1997, pp. 301-306
Objective.-To determine the excess length of stay, extra costs, and mo
rtality attributable to adverse drug events (ADEs) in hospitalized pat
ients. Design.-Matched case-control study. Setting.-The LDS Hospital,
a tertiary care health care institution. Patients.-All patients admitt
ed to LDS Hospital from January 1, 1990, to December 31, 1993, were el
igible. Cases were defined as patients with ADEs that occurred during
hospitalization; controls were selected according to matching variable
s in a stepwise fashion. Methods.-Controls were matched to cases on pr
imary discharge diagnosis related group (DRG), age, sex, acuity, and y
ear of admission; varying numbers of controls were matched to each cas
e. Matching was successful for 71% of the cases, leading to 1580 cases
and 20197 controls. Main Outcome Measures.-Crude and attributable mor
tality, crude and attributable length of stay, and cost of hospitaliza
tion. Results.-ADEs complicated 2.43 per 100 admissions to the LDS Hos
pital during the study period. The crude mortality rates for the cases
and matched controls were 3.5% and 1.05%, respectively (P<.001). The
mean length of hospital stay significantly differed between the cases
and matched controls (7.69 vs 4.46 days; P<.001) as did the mean cost
of hospitalization ($10 010 vs $5355; P<.001). The extra length of hos
pital stay attributable to an ADE was 1.74 days (P<.001). The excess c
ost of hospitalization attributable to an ADE was $2013 (P<.001). A li
near regression analysis for length of stay and cost controlling for a
ll matching variables revealed that the occurrence of an ADE was assoc
iated with increased length of stay of 1.91 days and an increased cost
of $2262 (P<.001). In a similar logistic regression analysis for mort
ality, the increased risk of death among patients experiencing an ADE
was 1.88 (95% confidence interval, 1.54-2.22; P<.001). Conclusion.-The
attributable lengths of stay and costs of hospitalization for ADEs ar
e substantial. An ADE is associated with a significantly prolonged len
gth of stay, increased economic burden, and an almost 2-fold increased
risk of death.