Comparison of two error-detection methods in a mail service pharmacy serving health facilities.

To compare two dispensing error-detection methods in a mail service pharmacy and explore clues to the causes of near errors.Descriptive and exploratory study.Mail service pharmacy serving health facilities, April 5-9, 2004.Technicians, pharmacists at a mail service pharmacy; nurses at health facilities served.Blinded, undisguised observation of prescription orders at a mail service pharmacy by a research pharmacist and student pharmacist.Prescription dispensing errors detected by pharmacist audit compared with errors reported by nurses at the health facilities served.Of the 3,337 prescription orders sampled, 16 (0.48%) contained one or more errors based on the observers' assessment and no errors were reported by nurses for these medications using incident reports. Error types detected by observation were compared with the data from incident reports for the 3 previous years. Extrapolating the findings of the observational study and comparing those data with the incident reports, significant differences were found for total dispensing errors, wrong strength errors, wrong dosage form errors, and wrong label instruction errors. Errors related to wrong drug were not significantly different between the observational and incidentreporting data. In observations of pharmacists at work in the mail-service pharmacy, proximity of look-alike/sound-alike drugs on storage shelves and inadequate lighting were potential causes of near errors.Pharmacist assessment of prescription orders detects more dispensing errors than nurse-based incident reports. The study identified clues to the causes of near errors occurring in a mail service pharmacy.