Once there is suspicion of delirium based on the presence of symptoms such as acute disturbance of attention, reduced environmental awareness and/or changes in cognition, the choice of screening tool is made based on the setting. The 4 A’s test (4AT) is a 4-item test used in general hospital settings. A score ≥4 indicates delirium is likely. Confusion assessment method (CAM)-based tools, such as the CAM, CAM-ICU, brief-CAM, paediatric-CAM and preschool-CAM, assess four features, Features A–D (or Features 1–4 depending on the specific tool). For delirium to be present according to CAM based tools, A and B must be present, plus either C or D. The Intensive Care Delirium Screening Checklist (ICDSC) is a delirium assessment tool measuring 8 domains, recorded as yes (present; score 1) or no (absent; score 0) answers. Delirium is likely for a score ≥4. The clinical tools described, except for ICDSC, are snapshot assessments. *depending on the tool used, Features A–D may be called 1–4 and will be assessed in different ways. DOB, date of birth; LOC, level of consciousness.