Unexpected effects of unintended consequences: EMR prescription discrepancies and hemorrhage in patients on warfarin.

Electronic prescribing can reduce certain types of medication errors but can also facilitate new types of errors. Internal prescription discrepancies arise when information in the structured (dose, frequency) fields conflicts with instructions given in the free-text field on the prescription, and are unique to electronic prescribing. It is not known whether internal prescription discrepancies lead to adverse events.We have conducted a case-control study to determine whether internal discrepancies in warfarin prescriptions are associated with an increased risk of hemorrhage. We compared frequency of internal discrepancies in warfarin prescriptions between 573 patients admitted for a major hemorrhage and 1,719 controls. In multivariable analysis case patients had the odds of 0.61 of having an internal discrepancy in the most recent warfarin prescription (p = 0.045) compared to controls.Consequences of EMR errors may not be obvious. Studies that directly examine clinical outcomes are necessary to identify categories of EMR errors likely to cause patient harm.