Clinical error severity rating scale
| Score | Rating of likely outcome | Description |
| 1 | Insignificant | Incident is likely to have little or no effect on the patient. |
| 2 | Minor outcome | Incident is likely to increase level of care, for example, review, investigations and referral to another clinician. |
| 3 | Moderate outcome | Incident is likely to lead to permanent reduction in bodily functioning, increased length of stay and surgery. |
| 4 | Major outcome | Incident is likely to lead to a major permanent loss of function. |
| 5 | Serious outcome | Incident is likely to lead to death. |
Errors with a score ≥3 were classed as potentially serious with potential for permanent harm.