The Precise Observation System for the Safe Use of Medicines (POSSUM): An Approach for Studying Medication Administration Errors in the Field.

Medication administration errors (MAEs) in hospital are frequent and significantly more likely to result in serious harm to patients than other medication error types. Many interventions have been proposed in order reduce MAEs and the amount of harm associated with these errors. A major limitation in assessing the effectiveness of these interventions has been the lack of robust measures for assessing changes in MAEs and associated harms. Drawing upon extensive foundational research we have developed a robust approach and data collection software to be applied in direct observational studies of nurses to allow measurement of changes in MAE rates. We report how this approach is being applied in a large stepped-wedge cluster randomised controlled trial to assess the effectiveness of an electronic medication management system to reduce MAEs in a paediatric hospital.