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CAM — Confusion Assessment Method
CAM Algorithm: Delirium = Feature 1 AND Feature 2 AND (Feature 3 OR Feature 4). Requires direct observation and informant input.
Clinical Assessment
1
Feature 1: Acute Onset & Fluctuating Course
Required
Is there evidence of an acute change in mental status from the patient's baseline? Does the abnormal behaviour fluctuate during the day (tends to come and go, or increase/decrease in severity)?
💡 Ask caregivers, nurses, or family: "Is this new/different for them?"
2
Feature 2: Inattention
Required
Did the patient have difficulty focusing attention? For example: easily distracted, or has difficulty keeping track of what is being said?
Was the patient's thinking disorganised or incoherent? For example: rambling or irrelevant conversation, unclear or illogical flow of ideas, or unpredictable switching from subject to subject?
💡 Feature 3 OR Feature 4 must be present (along with 1 and 2)
4
Feature 4: Altered Level of Consciousness
Overall, how would you rate this patient's level of consciousness? Anything other than alert (normal) qualifies.
💡 Vigilant = hyperalert; Lethargic = drowsy but arousable; Stuporous = difficult to arouse; Comatose
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Use
Suspected delirium in any hospitalised older adult — particularly post-operative.
Routine shift-by-shift delirium surveillance in geriatric, medical, and surgical wards.
Distinguishing delirium from dementia or acute psychiatric illness.
Gold Standard Bedside Tool
The CAM has sensitivity 94–100% and specificity 89–95% validated against DSM-III-R criteria. Endorsed by AGS, NICE, and the British Geriatrics Society.
Section 2
Formula & Logic
Diagnostic Algorithm
Delirium = Feature 1 AND Feature 2 AND (Feature 3 OR Feature 4)
Feature 1 — Acute Onset & Fluctuating Course (required)
Feature 2 — Inattention (required)
Feature 3 — Disorganised Thinking
Feature 4 — Altered Level of Consciousness
Feature Definitions
Feature 1
Mental status change from baseline; fluctuates during the day
Rambling or incoherent speech; illogical flow of ideas
Feature 4
Anything other than alert: vigilant, lethargic, stuporous, comatose
Section 3
Pearls/Pitfalls
Hypoactive Delirium — The Silent Killer
Hypoactive delirium (quiet, withdrawn, somnolent) is missed in up to 70% of cases without a structured tool. It carries a worse prognosis than hyperactive delirium and is more common in older adults on opioids or benzodiazepines.
Common Mimics to Exclude
Dementia — chronic, not acute; less attention fluctuation.
Depression — psychomotor slowing but attention intact.
Non-convulsive status epilepticus — requires EEG to exclude.
Section 4
Next Steps
CAM Positive — Immediate Actions
Section 5
Evidence Appraisal
Primary Reference
Clarifying confusion: the confusion assessment method.
Inouye SK et al. • Ann Intern Med.. 1990;113(12):941–948. Prospective validation across 2 cohorts; Se 94–100%, Sp 90–95%, vs. DSM-III-R criteria.
Section 6
Origins
Sharon Inouye — Yale University
Developed by Sharon Inouye at Yale University (1990). Created to address systematic under-detection of delirium in hospitalised older adults. Inouye subsequently led the Hospital Elder Life Program (HELP), a multicomponent delirium prevention programme implemented globally.
