guide to the 4at: INTRODUCTION
The 4 ‘A’s Test or 4AT is a quick and simple bedside test for delirium. It has 4 items:
[1] Alertness
[2] AMT4: Abbreviated Mental Test - 4.
[3] Attention test: Months of the Year Backwards
[4] Acute change or fluctuating course
The 4AT is designed to be simple to use and not to require special training. Yet some knowledge of delirium is essential when using the 4AT or other delirium tools: see here for a 5-minute video overview, or here for a more detailed written review.
4AT case examples: 6 cases (on a separate page) to demonstrate how the 4AT is scored in different situations.
Note: 4AT scoring of ‘untestable’ patients
Many patients with delirium are unable to produce meaningful speech because of drowsiness or severe inattention. A strength of the 4AT is that it allows these patients to have a score on the test. That is, if the patient cannot engage with the tester and attempt the AMT4 or the Attention test, then they are rated ‘untestable’ and given a score for this. Untestable status on both of these items yields a score of 4, which suggests possible delirium.
OVerview of scoring
The 4AT is scored from 0-12.
A score of 4 or more suggests delirium but is not diagnostic. In every case the diagnosis is reached by clinical judgement.
A score of 1-3 suggests cognitive impairment and more detailed cognitive testing and informant history-taking may be indicated.
A score of 0 does not definitively exclude delirium or cognitive impairment: more detailed testing may be needed depending on the clinical context.
The tester should take account of communication difficulties (hearing impairment, dysphasia, lack of common language) when carrying out the test and interpreting the score.
scoring 4AT ITEMS
Guide to scoring Item 1: altered level of alertness is >90% likely to be delirium in general hospital settings. If the patient shows significant altered alertness during the bedside assessment, score 4 for this item.
Guide to scoring Item 2: the Abbreviated Mental Test 4 or AMT4 is a brief test of orientation in which the patient is asked: age, date of birth, place (name of the hospital or building), and the current year. 1 mistake scores 1 point on the item, and 2 or more mistakes scores 2 points.
If the patient cannot provide meaningful answers because of altered arousal, inability to produce speech, etc., then the patient is given a score of 2 (given for patients who are ‘untestable’ on simple cognitive tests).
If the AMT10 (sometimes called the AMTS) is carried out before (e.g. as part of the Nottingham Hip Fracture Score), the AMT4 score can be extracted directly from items in the AMT10.
Guide to scoring Item 3: Months of the Year Backwards is a simple, widely-used test of attention which is sensitive to both delirium and general cognitive impairment. The patient is asked to recite the months of the year in backwards order from December.
If the patient verbally declines to start the test or is not able to correctly recite to June, score 1. If the patient cannot start the test for example through being drowsy or too inattentive they are in the ‘untestable’ category for this item and receive a score of 2.
Guide to scoring Item 4: rapid (hours, days) deterioration in mental functioning is highly specific to delirium. If there is evidence of change or fluctuation then this item scores 4. This gives an overall 4AT score of at least 4, indicating likely delirium.
Item 4 requires information from one or more source(s), eg. your own knowledge of the patient, other staff who know the patient (eg. ward nurses), GP letter, case notes, or carers.
As part of the process of determining change from baseline in non-cognitive areas it can be helpful to elicit any hallucinations and/or paranoid thoughts by asking the questions such as, “Are you concerned about anything going on here?”; “Do you feel frightened by anything or anyone?”; “Have you been seeing or hearing anything unusual?”
Fluctuation can occur without delirium in some cases of dementia, but marked fluctuation usually indicates delirium.
Note that Item 4 incorporates the ‘Single Question in Delirium’ or SQiD.
What if there is no informant history, or the informant history may not be reliable?
No informant history: it is common for there to be no carer available to give information on acute change or fluctuation. Some studies show that at the front door 25% of patients may have no informant. Often an informant can be contacted later, but this can delay a potential diagnosis if the assessment process requires an informant at the time of assessment.
Unreliable informant history: not all informants are able to provide a reliable history of change. For example, some relatives have very limited contact with patients, or some relatives may have cognitive impairment themselves. Therefore, all informant history needs to be used in the diagnostic process in the light of all sources of information and clinical judgement.
Clinical course strongly suggests mental status change: it can sometimes be determined by the practitioner that the observed mental status deterioration must be acute. For example, if the practitioner is seeing a patient who is drowsy but is known to be living independently before hospital admission, it is obvious that this is an acute change. In this situation, the practitioner should score Item 4 as a 4.
In summary, it is clear that in some situations in which there is no informant or no reliable informant it is clinically very likely that a patient has delirium. If a tool requires an informant history to give a final score, this creates a patient safety problem because requiring that an informant history is always required to make this diagnosis can lead to delayed diagnosis and treatment, a serious problem given that delirium is a medical emergency.
The 4AT was purposely designed to be robust to this, in that a score of 4/12 or more can be reached in several ways, even with no informant history:
Item 1 scoring 4
Items 2 & 3 both scoring 2
Item 4 scoring 4 using evidence from clinical history
This design feature of the 4AT reflects clinical practice, because practitioners do sometimes make a provisional diagnosis of delirium based on bedside features alone if no informant history is available. This reflects safe practice: while informant history should always be sought, a diagnosis of delirium should not be delayed if it is difficult or impossible to get this history immediately.
use of the 4AT in practice
The 4AT is used in the following situations:
ED or other acute settings as a screening tool for delirium in older people
At home or in care homes when delirium is a concern
Transitions of care
Pre-op delirium & cognitive assessment
Post-op, repeated daily for an appropriate period (usually 3-7 days)
Repeated daily during delirium to assess for recovery
At any time when delirium is suspected (e.g. with family concern, or if clinical observation is suggestive)
Note that multiple times per day monitoring for new-onset delirium in inpatients is best done with observational tools like the Single Question in Delirium (SQiD) or the National Early Warning Score - 2 (NEWS2).
The reason for using observational tools for monitoring is that asking patients to do repeated cognitive tests several times per day for periods of several days or more is too burdensome for both patients and staff. Compliance with tools that require this is usually poor. Even use of ‘ultra-brief’ cognitive tests multiple times per day is clinically inappropriate, not just because of patient and staff burden but because of practice effects.
In inpatients without delirium or in patients or residents in longer-term facilities, ongoing monitoring through observational tools is more appropriate than using cognitive tests multiple times per day. Several options for observational monitoring tools are available.
SQiD / NEWS2 as a monitoring tool with the 4AT as the follow-on delirium assessment tool is the recommended process in the UK National Health Service. See here for more details.