Tutorial on monitoring time to next medication error

Alemi and colleagues in this issue of the journal have proposed that rare events can be monitored by shifting from frequency of the event to the examination of the time to the event. This article examines their claim with data obtained from an acute care hospital in the United States. We examined the data on medication omissions to see whether changes in underlying process can be detected through control charts. Medication errors are rare; the article examines medication errors due to omission, which makes the phenomena rarer. The empirical question was whether changes in process of care could be detected using control charts from data on medication omissions. Two different types of control chart, the XmR and Tukey charts, were used to analyze the data. The control chart with the tightest control limits was chosen for further interpretation. The XmR chart showed that there was sufficient power to detect unusual days in which the time to omission error was higher than historical norm. This article suggests that even rare events can be monitored through judicious use of time to the event. It shows the viability of safety teams using time to sentinel events to monitor progress in reducing frequency of sentinel events.