4AT

Description

The 4AT is intended for delirium detection in general clinical settings, inpatient hospital areas outside the ICU, or in the community. Healthcare practitioners can use it without special training, and it takes roughly two minutes to complete. First published online in 2011, the test has 32 formal validation diagnostic test accuracy studies involving over 6000 patients. It has been evaluated in emergency departments, medical, surgical, community, and palliative care settings.

Internationally used in both clinical practice and research, the 4AT appears in clinical guidelines such as the UK NICE Guidelines on Delirium and in policy documents. It is also employed for delirium and cognitive assessment in hip fracture registries. Evidence indicates the 4AT can be implemented at scale in real-world practice, with positive score rates comparable to expected delirium prevalence. A large two-center study of 82,770 patients found that positive scores aligned with expected delirium rates and were linked to outcomes including 30-day and one-year mortality, hospital length of stay, and days at home after admission.

Parameters

The 4AT has four parameters: Alertness, Abbreviated mental test-4 (AMT4), Attention (months backwards test), and Acute change or fluctuating course. The total score ranges from 0 to 12, with 4 or more suggesting possible delirium and 1–3 suggesting possible cognitive impairment.

Parameters 1 and 4 can each individually trigger a positive score because altered arousal and acute change are highly specific for delirium. Parameters 2 and 3 provide embedded cognitive testing; if parameter 2 scores 2 or more mistakes or the patient is untestable, and parameter 3 shows untestability, the combined score is 4, indicating possible delirium. Untestability can trigger this outcome because many delirious patients are too drowsy or inattentive for cognitive testing, and these options allow completion in patients unable to give verbal responses.

Recommended use

The 4AT is intended for assessing delirium at initial presentation, during transitions of care, in high-risk periods such as post-operatively, and when delirium is suspected. Using it multiple times daily for prolonged monitoring of new onset delirium is not recommended due to the burden of repeated cognitive testing on patients and staff, though it can be used 1–2 times per day for specified periods like perioperatively. It is validated for monitoring recovery from active delirium and is considered an episodic rather than a monitoring test.

Multiple daily use may lower compliance and performance because of the burden of face-to-face interviews and cognitive testing. Shorter, largely observational tests such as NEWS2, RADAR, the Delirium Observation Scale, the Single Question in Delirium, or the Nursing Delirium Screening Scale are more suitable for ongoing routine monitoring after admission; a positive score on those typically requires a more detailed assessment with a tool like the 4AT. This area of practice needs additional research.

Did You Know?

• A review of data to December 2019 involving 17 studies reported a pooled sensitivity of 88% and a pooled specificity of 88% for delirium diagnosis.
• A large, high quality diagnostic randomized controlled trial comparing the 4AT and the Confusion Assessment Method found that the 4AT had higher sensitivity and similar specificity to the CAM.
• The 4AT has been translated into German, French, Italian, Spanish, Portuguese, Danish, Finnish, Swedish, Turkish, Arabic, Norwegian, Thai, Cantonese, Putonghua, Russian, Korean, Japanese, and Icelandic.