Table 2.

Incident severity classification system recommended by the National University Hospital Council of Japan

Level	Continuity of injury	Severity of injury	Outcome/Treatment of injury
Level 0	–	–	Error or trouble with a pharmaceutical or medical device was found, but did not affect the patient
Level 1	None	–	There was no harm to the patient (but there was a possibility of some influence)
Level 2	Transient	Mild	Treatment was not necessary (mild change in vital signs, need for increased patient observation, examination for confirmation of safety, etc.)
Level 3a	Transient	Moderate	Simple treatment was required (disinfection, poultice, skin suture, administration of analgesics, etc.)
Level 3b	Transient	Severe	Substantial treatment was required (significant change in vital signs, use of artificial respirator, surgery, prolongation of hospitalization, hospitalization, fracture, etc.)
Level 4a	Permanent	Mild to moderate	Permanent disability or subsequent complication remained, but was not accompanied by significant dysfunction or an aesthetic problem
Level 4b	Permanent	Moderate to severe	Permanent disability or subsequent complication remained, accompanied with significant dysfunction or an aesthetic problem
Level 5	Death	–	Death (excluding those due to the natural course of the underlying disease)