Frequency, type and clinical importance of medication history errors at admission to hospital: a systematic review.

BACKGROUND Over a quarter of hospital prescribing errors are attributable to incomplete medication histories being obtained at the time of admission. We undertook a systematic review of studies describing the frequency, type and clinical importance of medication history errors at hospital admission. METHODS We searched MEDLINE, EMBASE and CINAHL for articles published from 1966 through April 2005 and bibliographies of papers subsequently retrieved from the search. We reviewed all published studies with quantitative results that compared prescription medication histories obtained by physicians at the time of hospital admission with comprehensive medication histories. Three reviewers independently abstracted data on methodologic features and results. RESULTS We identified 22 studies involving a total of 3755 patients (range 33-1053, median 104). Errors in prescription medication histories occurred in up to 67% of cases: 10%- 61% had at least 1 omission error (deletion of a drug used before admission), and 13%- 22% had at least 1 commission error (addition of a drug not used before admission); 60%- 67% had at least 1 omission or commission error. Only 5 studies (n = 545 patients) explicitly distinguished between unintentional discrepancies and intentional therapeutic changes through discussions with ordering physicians. These studies found that 27%- 54% of patients had at least 1 medication history error and that 19%- 75% of the discrepancies were unintentional. In 6 of the studies (n = 588 patients), the investigators estimated that 11%-59% of the medication history errors were clinically important. INTERPRETATION Medication history errors at the time of hospital admission are common and potentially clinically important. Improved physician training, accessible community pharmacy databases and closer teamwork between patients, physicians and pharmacists could reduce the frequency of these errors.