To the Editor.
—Dr Bates et al1 and Dr Classen et al2 dem onstrated the significant impact of ADEs on length of stay and costs of hospitalizations. However, the reported economic burden of $4685 for preventable ADEs and $2595 for all ADEs in the article by Bates et al,1 and $2013 for all ADEs in the work by Classen et al,2 only consider adverse drug events that were acquired in hospitals. To put the consequences of ADEs during hospitalization in relation to all ADEs, it is necessary to quantify the burden of adverse events in ambulatory care as well.We performed a meta-analytic review of 21 original studies published from 1975 through 1996 and identified 13 reports in adults admitted to medical or emergency services because of ADEs in 4 industrialized countries or regions (United States 3, Europe 8, South Africa 1, Taiwan 1). The meta-analysis used the World