Table 1

Description of categories of harm and preventability scale

Category/classDescription
Level of harm
 ACircumstances or events that have the capacity to cause error
 BAn error occurred but the error did not reach the patient
 CAn error occurred that reached the patient but did not cause the patient harm
 DAn error occurred that reached the patient and required monitoring to confirm that it resulted in no harm to the patient and/or required intervention to preclude harm
 EAn error that contributed to or resulted in temporary harm to the patient and required intervention
 FAn error that contributed to or resulted in temporary harm to the patient and required initial or prolonged hospitalisation
 GAn error that contributed to or resulted in permanent patient harm
 HAn error that required intervention necessary to sustain life
 IAn error that may have contributed to the patient's death
Preventability scale
 1No real evidence for preventability
 2Weak to small evidence for preventability
 3Preventability less likely than 50%, but close
 4Preventability more probable than 50%, but close
 5Strong evidence for preventability
 6Completely secure evidence for preventability
  • Only categories E–I are included in the global trigger tool, because it is designed to identify injury to the patient.

  • Classes 1–3 are considered non-preventable harm.

  • Classes 4–6 are considered preventable harm.