Table 1 Delirium screening tool comparisons

4 ‘A’s test (4AT)

Four cognitive domains are rapidly assessed in the clinical setting: alertness, orientation, attention, and acute change/fluctuating course. A final score is provided, with scores ≥ 4 points indicating possible delirium (± cognitive impairment) and scores 1–3 indicating possible cognitive impairment. Pooled sensitivity and specificity across various clinical settings are each approximately 88% [14, 18].

Nursing Delirium Screening Scale (NuDesc)

This is a tool designed for nurses to complete at the end of each shift, drawing from their experiences throughout the shift. The screening tool includes assessment of five relevant areas of cognition and arousal: disorientation, inappropriate behaviour, inappropriate communication, illusions/hallucinations, and psychomotor retardation. A continuous score is provided, but a threshold (≥ 2) suggests delirium presence. Sensitivity approximately 86%, specificity 87% [15].

Confusion Assessment Method (CAM)

The Confusion Assessment Method (CAM) conventionally consists of a formal cognitive function assessment paired with subsequent diagnostic algorithm for determining delirium. Multiple cognitive domains are assessed, and the final diagnostic algorithm is based on acute change, fluctuating course, inattention, disorganized thinking, and altered level of consciousness. Sensitivity from pooled high-quality studies is approximately 82% with specificity of 99% [19]. Using the CAM based on bedside observations alone, without cognitive function testing, renders a lower sensitivity (19 − 67%) but a preserved specificity (91–98%) [20, 21].