Table 2 Diagnostic criteria for delirium³,¹²,¹⁴,¹⁵.

DSM IV criteria	Confusion assessment method criteria
1. Disturbance of consciousness with impaired ability to focus or shift attention	1. Acute onset and fluctuating course: Is there an acute change in mental state from the patient's baseline? Does the abnormal behaviour fluctuate?
2. Change in cognition (memory impairment, disorientation, language disturbances, perceptual disturbances)	2. Inattention: Does the patient have difficulty focusing attention (ie, easily distracted)?
3. Disturbance evolves over a short period of time (hours/days) and fluctuates during the course of the day	3. Disorganised thinking: Was the patient's thinking disorganised (ie, rambling or irrelevant conversation, illogical flow of ideas)?
4. Evidence of a general medical condition, substance intoxication or withdrawal judged to be aetiologically related to the disturbance	4. Altered level of consciousness, eg, hyperalert, lethargic, stupor or comatosed
To diagnose delirium all 4 features must be present	To diagnose delirium features 1 and 2 and either 3 or 4 must be present

DSM IV, Diagnostic and statistical manual of mental disorders, 4th ed.