Table 2 Categories of harm adapted from the National Coordinating Council for Medication Error Reporting and Prevention (NCC MERP) Index

Excluded
Category A	Circumstances or events that have the capacity to cause error
Category B	An error that did not reach the patient
Category C	An error that reached the patient but did not cause harm
Category D	An error that reached the patient and required monitoring or intervention to confirm that it resulted in no harm to the patient
Categories used for adverse events
Category E	Temporary harm to the patient and required intervention
Category F	Temporary harm to the patient and required initial or prolonged hospitalisation
Category G	Permanent patient harm
Category H	Intervention required to sustain life
Category I	Patient death

Note that NCC MERP’s “An error that contributed to or resulted in …” has been deleted in the Institute for Healthcare Improvement’s adaptation of categories E–I, because Trigger Tools are designed to find harm, whether or not the result of an error.