4AT

The 4 'A's Test (4AT) is a bedside medical scale used to help determine if a person has positive signs for delirium.^[1][2] The 4AT also includes cognitive test items, making it suitable also for use as a rapid test for cognitive impairment.^[3]

The 4AT is designed to be used as a delirium detection tool in general clinical settings, inpatient hospital settings outside of the Intensive Care Unit (ICU), or in the community. The 4AT is intended to be used by healthcare practitioners without the need for special training, and it takes around two minutes to complete.^[4] The test was first published online in 2011; the 4AT website provides downloads, and a guide to the test along with case examples.^[4] The 4AT is also available as a standalone app on the Android and iOS platforms, and as an online calculator.

The 4AT has the most published diagnostic test accuracy data of any delirium tool, with >25 published studies involving >5000 observations.^[5] It has been evaluated in multiple areas of practice including in the emergency department (ED), medical, surgical, community and palliative care settings.^[6][7][8] The 4AT is used internationally in both clinical practice^{[9][10][11][12][13][14]} and research.^{[15][16][17][18]} It is recommended in clinical guidelines, including the UK NICE Guidelines on Delirium, and policy documents.^{[19][20][21][22][23][24]}

Some evidence shows that the 4AT can be implemented at scale in real-world clinical practice and that it shows positive score rates at comparable levels to the expected delirium prevalence rates.^[25][26]

A 2022 two-center study in real-world clinical populations (total N=82,770) found that 4AT positive scores were aligned with expected delirium rates, and also were strongly linked with important outcomes including 30-day mortality, one-year mortality, hospital length of stay, and days at home in the year following hospital admission. Notably, the 4AT was completed as part of usual care by a large number of different staff (mostly doctors and nurses) who had not received special training in use of the 4AT. This study therefore showed that the 4AT is feasible in large-scale practice and that it provides real-time delirium ascertainment with positive scores being linked to important short and longer-term outcomes.^[26]