4AT Calculator — Rapid Delirium and Cognitive Impairment Test
Score the 4AT rapid delirium screen — alertness, AMT4, months of the year backwards and acute change or fluctuating course — 0 to 12, with the cut-off of 4 or more for possible delirium.
How it works
4AT = alertness (normal or brief mild sleepiness 0, clearly abnormal 4) + AMT4 (0 / 1 / 2) + months backwards (0 / 1 / 2) + acute change or fluctuation (0 or 4); total 0–12. 4 or more: possible delirium ± cognitive impairment · 1–3: possible cognitive impairment · 0: delirium or severe cognitive impairment unlikely.
The 4AT (Bellelli et al., Age and Ageing 2014; validated in a large multicenter study by Tieges et al. 2021) is a short delirium screen that takes under two minutes and needs no special training. It is used in emergency departments, acute medical and surgical wards and hip-fracture care, and it can be completed in drowsy or agitated patients who could not do a longer test, because being untestable is itself scored. A score of 4 or more suggests delirium but is not diagnostic; a full clinical assessment should follow. A score of 0 does not rule out delirium if the history of acute change is incomplete.
Worked example
An 84-year-old on a surgical ward is fully alert (0), gets the year wrong on the AMT4 (1 mistake: 1), and gives the months backwards only as far as August (fewer than 7 correct: 1); the family reports no acute change (0): 4AT = 0 + 1 + 1 + 0 = 2 / 12 — possible cognitive impairment, not delirium.
Sources: Bellelli G et al. Validation of the 4AT, a new instrument for rapid delirium screening. Age Ageing 2014;43:496–502 · Tieges Z et al. Diagnostic accuracy of the 4AT for delirium detection in older adults: systematic review and meta-analysis. Age Ageing 2021 · The 4AT — official test and guidance
Frequently asked questions
What does a 4AT score of 4 or more mean?
It suggests possible delirium, with or without underlying cognitive impairment. Because delirium is a medical emergency, the patient needs a full clinical assessment and a search for causes such as infection, drugs, dehydration or pain.
What is the AMT4?
The four-item Abbreviated Mental Test: age, date of birth, place (name of the hospital or building) and current year. One point is scored for one mistake and two points for two or more mistakes or if the patient cannot be tested.
Can the 4AT be used in drowsy patients?
Yes. Unlike many cognitive tests, the 4AT scores clear drowsiness as abnormal alertness (4 points), and inability to attempt the test items is scored as well.
Does the 4AT need training or a license?
No formal training is needed and the test is free to use; instructions are available at the4at.com.
Related calculators
Clinical decision tool for education and for use by trained clinicians alongside clinical judgement — not a diagnosis and not a substitute for medical assessment. Scores and cut-offs come from the cited validation studies and may not apply to every patient; follow local protocols.