How useful are voluntary medication error reports? The case of warfarin-related medication errors

A study was conducted to explore the value and limitations of voluntary medical error reports and to learn about common errors in warfarin use.

Voluntary reports of 8,837 inpatient errors and 820 outpatient errors in warfarin use submitted by 445 hospitals and 192 outpatient facilities participating in MEDMARX, a voluntary medication error reporting system, from 2002 to 2004, were gathered.

Overall, errors occurred most often during transcription/documentation (35%) and administration (30%) in hospitals, and during prescribing (31%) and dispensing (39%) in outpatient settings. Dosing errors were the most common type. In hospitals, more than 50% of reported errors were initiated by nurses, and 50% were intercepted by nurses, whereas in outpatient settings, about 50% of reported errors occurred in pharmacies and 50% were intercepted by pharmacists. About 17% of inpatient and 13% of outpatient warfarin errors resulted in changes in patient care, and 42% of inpatient and 62% of outpatient errors resulted in procedural changes. Cascade analysis and textual descriptions further located specific, correctible safety lapses.

Voluntary medical error reporting systems can, to some extent, provide meaningful and actionable information to guide patient safety improvement, but their usefulness is limited because of a lack of details, incomplete reporting, underreporting, and various reporting biases.