Rating scales in delirium

Purpose and classification. Scales are used to overcome the fact that delirium is under-recognised in up to two-thirds of cases. They fall into four groups: (i) screening/detection tools, (ii) diagnostic criteria-based instruments, (iii) severity scales for monitoring response, and (iv) prediction models. A scale screens; DSM-5 or ICD-10 diagnoses.

Screening/detection tools (Pathy list, chronological): SPMSQ, Delirium Rating Scale (DRS), Confusion Assessment Method (CAM), Delirium Symptom Interview, Delirium Assessment Scale, Cognitive Test for Delirium (CTD), NEECHAM Confusion Scale, Confusional State Evaluation, Memorial Delirium Assessment Scale (MDAS), Delirium Index, Delirium Severity Scale, CAM-ICU, DRS-R-98, Delirium Detection Score, DDT-Pro, bCAM, 4AT, and the Stanford Proxy Test for Delirium (S-PTD).

Ward tools. CAM is the most widely used (sensitivity 94%, specificity 89%). 3D-CAM is a scripted 3-minute version — sensitivity 96% / specificity 86% in dementia, and 93% / 96% without dementia. 4AT takes under 2 minutes, needs no special training and works in drowsy or untestable patients, which is why NICE and SIGN recommend it. bCAM is the brief emergency-department version.

Ultra-brief screens. The best single item is "months of the year backwards" (sensitivity 83%, specificity 69%). The best two-item screen (UB-2) is "months of the year backwards" + "what is the day of the week?" (sensitivity 93%, specificity 64%). High sensitivity with low specificity means these are rule-out tools; a positive result demands fuller assessment.

ICU and dementia-specific tools. CAM-ICU is used in intubated or non-verbal patients: inattention is tested with the letter task ("squeeze my hand for the letter A" → SAVEAHAART), altered consciousness is any RASS score other than 0, and disorganised thinking uses yes/no questions. For delirium superimposed on dementia, the best single item is "What day of the week is it?", the best two-item screen adds days of the week backwards, and the best three-item screen adds "What type of place is this?" and "Does the patient appear sleepy?"; sensitivities are 84%, 93% and 94% but specificities only 41%, 30% and 42%.

Severity and prediction; frequency of use. Severity and trajectory are tracked with the MDAS, DRS-R-98, Delirium Index and Delirium Severity Scale — useful in palliative care and research. Risk prediction uses the E-PRE-DELIRIC model and Stanford's Algorithm for Predicting Delirium (SAPD), which allow preventive resources to be targeted. Screening frequency: daily in hospital, weekly in post-acute care, monthly in long-term care, and at any reported change from baseline.

NICE CG103 (January 2023) issued new recommendations specifically on assessing and diagnosing delirium and established the 4AT as the recommended short assessment tool in both NICE and SIGN guidance — a definite shift away from CAM-only teaching, because the 4AT requires no training and can be completed in patients too drowsy to be formally tested. The APA 2025 guideline reinforces this by requiring systematic tool-based screening of at-risk patients rather than clinical impression, and adds assessment at transitions of care, including before discharge.