4AT Delirium Assessment Calculator

A rapid bedside screening tool for delirium detection, validated for use in general hospital settings. Recommended by NICE guidance NG97.

Important Clinical Disclaimer: The 4AT assessment is intended for use by qualified healthcare professionals only. It is for educational and informational purposes and should not replace clinical judgement. Always interpret results alongside the full clinical picture and follow your local guidelines and protocols.
4AT Assessment

This includes patients who may be markedly drowsy (e.g., difficult to rouse and/or obviously sleepy during assessment) or agitated/hyperactive. Observe the patient. If asleep, attempt to wake with speech or gentle touch on shoulder. Ask the patient to state their name and address to assist rating.

Ask the patient the following questions:

  • Age
  • Date of birth
  • Place (name of the hospital or building)
  • Current year

Ask the patient: "Please tell me the months of the year in backwards order, starting at December."

To assist initial understanding, one prompt of "what is the month before December?" is permitted.

Evidence of significant change or fluctuation in: alertness, cognition, other mental function (e.g., paranoia, hallucinations) arising over the last 2 weeks and still evident in last 24hrs.

About the 4AT

The 4AT is a validated screening instrument designed for rapid initial assessment of delirium and cognitive impairment. It was developed by clinicians at NHS Lothian and the University of Edinburgh.

Key Features:
  • Takes approximately 2 minutes to complete
  • Requires no special training
  • Can be used in patients who are unable to speak or are too unwell to be tested
  • Validated in multiple clinical settings
  • Recommended by NICE NG97 and Scottish Intercollegiate Guidelines Network (SIGN)
When to Use:
  • On admission to hospital
  • When delirium is suspected
  • As part of routine cognitive screening in older patients
  • Following surgery or during acute illness

4AT Score Interpretation

4AT Score Interpretation Recommended Action
0 Delirium or severe cognitive impairment unlikely
  • Delirium unlikely (but still possible if Item 4 information incomplete)
  • Continue clinical observation as appropriate
  • Consider other causes of any presenting symptoms
1-3 Possible cognitive impairment
  • More detailed cognitive testing required
  • Consider formal dementia assessment if appropriate
  • May indicate delirium, especially if score driven by Item 4
  • Consider informant history for baseline cognition
4 or more Possible delirium ± cognitive impairment
  • Delirium assessment required - assess for underlying cause
  • Initiate delirium management pathway
  • Consider urgent medical review
  • Review medications, infection, metabolic causes
  • Document baseline cognition from informant
Important Notes:
  • A score of 4+ suggests delirium is possible, not certain. Further assessment is always required.
  • The 4AT does not distinguish between delirium and dementia - patients with dementia may score ≥4.
  • For patients with known dementia, focus particularly on Item 4 (acute change) to detect superimposed delirium.
  • Repeat testing may be needed as delirium can fluctuate.

Limitations

When the 4AT May Be Less Reliable
  • Severe hearing impairment - may affect AMT4 and attention testing
  • Pre-existing severe dementia - baseline score may already be elevated
  • Aphasia or dysarthria - may affect verbal responses
  • Non-English speakers - ensure appropriate translation/interpretation
  • Learning disabilities - baseline cognition may affect scores
  • Psychiatric conditions - may affect alertness and attention
What the 4AT Does NOT Do
  • Does not diagnose delirium - it is a screening tool
  • Does not replace comprehensive delirium assessment (e.g., DSM-5, CAM)
  • Does not identify the cause of delirium
  • Does not distinguish delirium subtypes (hypoactive vs hyperactive)
  • Does not replace clinical judgement
  • Does not monitor delirium severity over time

Frequently Asked Questions

The "4AT" refers to the four items assessed in the tool: Alertness, AMT4 (cognitive testing), Attention, and Acute change or fluctuation. The name also indicates it takes approximately 4 minutes or less to administer (typically around 2 minutes).

The 4AT has been validated in multiple studies with reported sensitivity of approximately 76-93% and specificity of approximately 70-94% for detecting delirium. A 2021 systematic review found pooled sensitivity of 88% and specificity of 88%. It performs comparably to other screening tools like the CAM but is faster to administer.

Yes, but with caution. Patients with dementia may score ≥1 at baseline due to cognitive impairment. The key is to focus on Item 4 (Acute Change) - any new or worsening symptoms over the past 2 weeks may indicate delirium superimposed on dementia. Obtaining baseline cognitive status from family/carers is essential.

A score of 4+ indicates possible delirium. Recommended actions include:

  • Initiate your local delirium pathway/protocol
  • Search for underlying causes (infection, medications, metabolic disturbance, pain, constipation, urinary retention)
  • Implement non-pharmacological interventions (orientation, sleep hygiene, mobilisation)
  • Review and rationalise medications
  • Arrange medical review
  • Document findings and communicate with the team

There is no fixed rule, but consider repeating:

  • Daily in high-risk patients or those with delirium
  • When there is clinical concern about change in mental state
  • Post-operatively (especially in older patients)
  • Following any significant clinical change

Delirium fluctuates, so a single normal score does not exclude delirium if clinical suspicion remains.

Disclaimer

This calculator is provided for educational and informational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment.

  • Always seek the advice of a qualified healthcare provider with any questions regarding a medical condition.
  • Never disregard professional medical advice or delay seeking it because of information from this tool.
  • Clinical decision-making should always incorporate the full clinical context, patient preferences, and local protocols.
  • The creators of this tool accept no liability for decisions made based on its output.

If you are a patient: please discuss any results with your healthcare provider. This tool is designed for use by medical professionals and may not be appropriate for self-assessment.

References

  1. Bellelli G, et al. (2014). Validation of the 4AT, a new instrument for rapid delirium screening: a study in 234 hospitalised older people. Age and Ageing, 43(4), 496-502.
  2. MacLullich AMJ, et al. (2019). The 4AT Rapid Clinical Test For Delirium. Official 4AT website.
  3. NICE (2023). Delirium: prevention, diagnosis and management in hospital and long-term care (NG97).
  4. Shenkin SD, et al. (2019). Diagnostic accuracy of the 4AT for delirium detection in older adults: systematic review and meta-analysis. Age and Ageing, 48(2), 311-320.
  5. Scottish Intercollegiate Guidelines Network (SIGN). (2019). SIGN 157: Risk reduction and management of delirium.