Confusion Assessment Method (CAM) Calculator

inputs

Feature 1: Acute onset and fluctuating course
Is there evidence of acute change in mental status from baseline? Does the abnormal behaviour fluctuate during the day?

Feature 2: Inattention
Does the patient have difficulty focusing attention (e.g., easily distracted, difficulty keeping track of conversation)?

Feature 3: Disorganised thinking
Is the patient's thinking disorganised or incoherent (e.g., rambling, irrelevant conversation, illogical flow of ideas, unpredictable switching)?

Feature 4: Altered level of consciousness
Any level other than alert (vigilant/hyperalert, lethargic, stupor, coma)

✓ when to use

Use in any hospitalised patient (particularly elderly) with suspected delirium or acute change in mental status. Appropriate for ED, ward, ICU (use CAM-ICU variant), and post-operative settings. Screen on admission and when acute confusion develops. NICE recommends delirium screening for at-risk patients.

✗ when not to use

CAM requires an assessor who understands the patient's baseline mental status — it is less reliable without collateral history. May miss hypoactive (quiet) delirium if not specifically assessed. CAM does not distinguish delirium from dementia in patients with pre-existing cognitive impairment — though both may coexist. For intubated/ICU patients, use CAM-ICU (modified for non-verbal assessment).

clinical pearls

CAM requires Feature 1 (acute onset/fluctuation) AND Feature 2 (inattention) PLUS either Feature 3 (disorganised thinking) OR Feature 4 (altered consciousness). All four features are assessed, but the diagnostic algorithm is specific.
Inattention is the cardinal feature of delirium. Test by asking the patient to recite months of the year backwards, or to count backwards from 20. Difficulty with these simple tasks in a previously cognitively intact patient strongly suggests delirium.
Hypoactive delirium (withdrawn, quiet, drowsy) is frequently missed because the patient is not 'confused' in the typical disruptive sense. Always consider delirium in any acutely drowsy or withdrawn elderly patient.
Delirium is a medical emergency with an underlying cause. The mnemonic PINCH ME covers common precipitants: Pain, Infection, Nutrition, Constipation, Hydration, Medication, Environment.
Delirium and dementia frequently coexist. A patient with known dementia can develop superimposed delirium — in fact, dementia is the strongest risk factor for delirium. Establish baseline cognitive function from carers.

✓ when to use

✗ when not to use

clinical pearls

CAM requires Feature 1 (acute onset/fluctuation) AND Feature 2 (inattention) PLUS either Feature 3 (disorganised thinking) OR Feature 4 (altered consciousness). All four features are assessed, but the diagnostic algorithm is specific.
Inattention is the cardinal feature of delirium. Test by asking the patient to recite months of the year backwards, or to count backwards from 20. Difficulty with these simple tasks in a previously cognitively intact patient strongly suggests delirium.
Hypoactive delirium (withdrawn, quiet, drowsy) is frequently missed because the patient is not 'confused' in the typical disruptive sense. Always consider delirium in any acutely drowsy or withdrawn elderly patient.
Delirium is a medical emergency with an underlying cause. The mnemonic PINCH ME covers common precipitants: Pain, Infection, Nutrition, Constipation, Hydration, Medication, Environment.
Delirium and dementia frequently coexist. A patient with known dementia can develop superimposed delirium — in fact, dementia is the strongest risk factor for delirium. Establish baseline cognitive function from carers.

Confusion Assessment Method (CAM)

inputs

✓ when to use

✗ when not to use

clinical pearls

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