4AT (Bellelli)

4AT

Sum the Bellelli 2014 4AT items and return unlikely (0), possible cognitive impairment (1–3), or possible delirium (≥4).

LIVE $0.005 USDC GET /api/calc/4at

Markdown: /docs/4at.md · Canonical: https://magentlab.com/docs/4at

Not a medical device. Not a diagnosis, dose, or listing recommendation.

What it computes

Sum the Bellelli 2014 4AT items and return unlikely (0), possible cognitive impairment (1–3), or possible delirium (≥4).

When to use

When an agent already has 4AT items assigned as in Bellelli 2014 and needs the published total and band, not a delirium or dementia diagnosis.

When not to use

Not a medical device and not a delirium or dementia diagnosis. magent does not examine the patient.
AMT4 is a caller-assigned mistake count (0, 1, or 2). The paper’s AMT4 asks age, date of birth, place, and year at the bedside; this API does not collect those.
Alertness, attention, and acute change or fluctuation are caller-assigned. magent does not observe consciousness, run months backwards, or take a history.
Score 0 is unlikely, 1–3 is possible cognitive impairment, and ≥4 is possible delirium. This is a screening total, not a diagnosis.

Formula

4AT = alertness (normal 0, abnormal 4) + amt4 (0/1/2) + attention (0/1/2) + acute_change (false 0, true 4); Bellelli 2014; max 12; 0 unlikely, 1-3 possible_cognitive_impairment, ≥4 possible_delirium

Citation

Title: Validation of the 4AT, a new instrument for rapid delirium screening: a study in 234 hospitalised older people
Authors: Bellelli G, Morandi A, Davis DH, Mazzola P, Turco R, Gentile S, Ryan T, Cash H, Guerini F, Torpilliesi T, Del Santo F, Trabucchi M, Annoni G, MacLullich AM
Source: Age Ageing. 2014;43(4):496-502
DOI: 10.1093/ageing/afu021

Worked example

All items zero

Given: acute_change=falsealertness=normalamt4=0attention=0

alertness normal → 0; amt4 0; attention 0; acute_change false → 0
Score = 0 (max 12); at_band = unlikely

All items maximum

Given: acute_change=truealertness=abnormalamt4=2attention=2

alertness abnormal → 4; amt4 2; attention 2; acute_change true → 4
Score = 12 (max 12); at_band = possible_delirium

Also searched as

4AT
4 A's Test
4AT delirium
Bellelli 4AT
AMT4 delirium screen
four AT
rapid delirium screening
4AT cognitive test

Try

Opens the live endpoint. Unpaid browser requests show the paywall; agents should send Accept: application/json.

/api/calc/4at?alertness=normal&amt4=0&attention=0&acute_change=false

Full URL: https://api.magentlab.com/api/calc/4at?alertness=normal&amt4=0&attention=0&acute_change=false

Call

Expect HTTP 402 until you retry with PAYMENT-SIGNATURE. Incomplete query params return HTTP 400 before any quote or charge.

curl -i -H "Accept: application/json" "https://api.magentlab.com/api/calc/4at?alertness=normal&amt4=0&attention=0&acute_change=false"

Parameters

Name	Type	Required	Description
`alertness`	string	required · normal, abnormal	Bellelli 2014 4AT item 1 as assigned by the caller. normal scores 0; abnormal scores 4. magent does not observe consciousness.
`amt4`	integer	required · 0, 1, 2	Caller-assigned AMT4 mistake count only (Bellelli 2014): 0 mistakes → 0; 1 mistake → 1; ≥2 mistakes or untestable → 2. Integer 0, 1, or 2. This API does not collect age, date of birth, place, or year.
`attention`	integer	required · 0, 1, 2	Bellelli 2014 months-backwards item as assigned by the caller. 0: achieves ≥7 months. 1: starts but <7 months or refuses. 2: untestable. Integer 0, 1, or 2. magent does not run months backwards.
`acute_change`	boolean	required	Bellelli 2014 acute change or fluctuating course as assigned by the caller. true scores 4. magent does not take a collateral history.

Bulk (POST)

POST the same path with a JSON items array. The first item is the GET unit; each additional item is $0.002. Invalid items return HTTP 400 before settlement.

POST /api/calc/4at Max 25 unit_amount + extra_item_amount * (n - 1) extra $0.002 PREVIEW

1 to 25 items. Each item uses the same keys as the GET query parameters.
POST of 1 item costs the same as GET. Lists longer than 25: chunk into multiple POSTs. Extra items still execute; do not pad dummy rows.
The first invalid item fails the whole request (index in the 400 JSON). You are not charged.
HTTP 200 is {count, path, items}. Each items[i] is the GET 200 body for that row.
Catalog misses (empty matches, found=false) stay paid 200s inside that slot.
x402 resource URL is this path plus n and body_sha256. Browsers that prefer text/html get the same paywall as GET; Pay retries POST with the same items.

Example request (fixture)

{
  "items": [
    {
      "acute_change": "false",
      "alertness": "normal",
      "amt4": "0",
      "attention": "0"
    },
    {
      "acute_change": "false",
      "alertness": "normal",
      "amt4": "0",
      "attention": "0"
    }
  ]
}

Open bulk paywall →

Opens a two-item fixture on the API host. Unpaid browsers get the same MetaMask paywall as GET; Pay retries POST with those items.

Example 200 (fixture)

{
  "count": 2,
  "path": "/api/calc/4at",
  "items": [
    {
      "components": [
        {
          "factor": "alertness",
          "points": 0,
          "present": false
        },
        {
          "value": 0,
          "factor": "amt4",
          "points": 0,
          "present": false
        },
        {
          "value": 0,
          "factor": "attention",
          "points": 0,
          "present": false
        },
        {
          "factor": "acute_change",
          "points": 0,
          "present": false
        }
      ],
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Bellelli G, Morandi A, Davis DH, Mazzola P, Turco R, Gentile S, Ryan T, Cash H, Guerini F, Torpilliesi T, Del Santo F, Trabucchi M, Annoni G, MacLullich AM",
        "doi": "10.1093/ageing/afu021",
        "id": "bellelli-2014",
        "pmid": "24590568",
        "source": "Age Ageing. 2014;43(4):496-502",
        "title": "Validation of the 4AT, a new instrument for rapid delirium screening: a study in 234 hospitalised older people"
      },
      "formula": "4at",
      "formula_expression": "4AT = alertness (normal 0, abnormal 4) + amt4 (0/1/2) + attention (0/1/2) + acute_change (false 0, true 4); Bellelli 2014; max 12; 0 unlikely, 1-3 possible_cognitive_impairment, ≥4 possible_delirium",
      "max_score": 12,
      "score": 0,
      "at_band": "unlikely"
    },
    {
      "components": [
        {
          "factor": "alertness",
          "points": 0,
          "present": false
        },
        {
          "value": 0,
          "factor": "amt4",
          "points": 0,
          "present": false
        },
        {
          "value": 0,
          "factor": "attention",
          "points": 0,
          "present": false
        },
        {
          "factor": "acute_change",
          "points": 0,
          "present": false
        }
      ],
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Bellelli G, Morandi A, Davis DH, Mazzola P, Turco R, Gentile S, Ryan T, Cash H, Guerini F, Torpilliesi T, Del Santo F, Trabucchi M, Annoni G, MacLullich AM",
        "doi": "10.1093/ageing/afu021",
        "id": "bellelli-2014",
        "pmid": "24590568",
        "source": "Age Ageing. 2014;43(4):496-502",
        "title": "Validation of the 4AT, a new instrument for rapid delirium screening: a study in 234 hospitalised older people"
      },
      "formula": "4at",
      "formula_expression": "4AT = alertness (normal 0, abnormal 4) + amt4 (0/1/2) + attention (0/1/2) + acute_change (false 0, true 4); Bellelli 2014; max 12; 0 unlikely, 1-3 possible_cognitive_impairment, ≥4 possible_delirium",
      "max_score": 12,
      "score": 0,
      "at_band": "unlikely"
    }
  ]
}

Response

Field	Type	Description
`formula`	string	4at
`formula_expression`	string	Exact expression used
`score`	integer	4AT points 0-12
`max_score`	integer	Always 12
`at_band`	string	unlikely when score is 0, possible_cognitive_impairment when 1-3, possible_delirium when ≥4 (Bellelli 2014). Not a delirium diagnosis.
`components`	array	Per-item points
`citation`	object	Bellelli 2014 Age Ageing citation
`disclaimer`	string	Not-a-device notice

Example JSON

Machine form of the same example. Frozen fixture. Not a live lookup.

{
  "components": [
    {
      "factor": "alertness",
      "points": 0,
      "present": false
    },
    {
      "value": 0,
      "factor": "amt4",
      "points": 0,
      "present": false
    },
    {
      "value": 0,
      "factor": "attention",
      "points": 0,
      "present": false
    },
    {
      "factor": "acute_change",
      "points": 0,
      "present": false
    }
  ],
  "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
  "citation": {
    "authors": "Bellelli G, Morandi A, Davis DH, Mazzola P, Turco R, Gentile S, Ryan T, Cash H, Guerini F, Torpilliesi T, Del Santo F, Trabucchi M, Annoni G, MacLullich AM",
    "doi": "10.1093/ageing/afu021",
    "id": "bellelli-2014",
    "pmid": "24590568",
    "source": "Age Ageing. 2014;43(4):496-502",
    "title": "Validation of the 4AT, a new instrument for rapid delirium screening: a study in 234 hospitalised older people"
  },
  "formula": "4at",
  "formula_expression": "4AT = alertness (normal 0, abnormal 4) + amt4 (0/1/2) + attention (0/1/2) + acute_change (false 0, true 4); Bellelli 2014; max 12; 0 unlikely, 1-3 possible_cognitive_impairment, ≥4 possible_delirium",
  "max_score": 12,
  "score": 0,
  "at_band": "unlikely"
}

Client errors (HTTP 400)

Invalid params return 400 without charge. Shared HTTP 402 and 503 meanings: Payments.

HTTP	Code	When
400	`invalid_alertness`	alertness must be normal or abnormal (Bellelli 2014 4AT item 1). Returned before settlement; you are not charged.
400	`invalid_amt4`	amt4 must be 0, 1, or 2 (Bellelli 2014 4AT; 2 is ≥2 mistakes or untestable). Returned before settlement; you are not charged.
400	`invalid_attention`	attention must be 0, 1, or 2 (Bellelli 2014 4AT months backwards; 2 is untestable). Returned before settlement; you are not charged.
400	`invalid_flag`	boolean clinical flags must be true or false Returned before settlement; you are not charged.
400	`invalid_items`	POST body must be a JSON object with only an items array Returned before settlement; you are not charged.
400	`invalid_item_count`	items must be an array of 1 to 25 objects Returned before settlement; you are not charged.
400	`invalid_item`	each items entry must be a JSON object Returned before settlement; you are not charged.

Related tools

CAM-ICU — Apply the Ely 2001 CAM-ICU algorithm and return whether delirium is present from four caller-assigned features.
RASS — Return the Sessler 2002 Richmond Agitation-Sedation Scale term and description from a caller-assigned integer -5 to +4.
Glasgow Coma Scale — Compute the Glasgow Coma Scale as the sum of caller-assigned eye, verbal, and motor integers. The 1974 or 1976 edition is required.

Payment

Unpaid requests return HTTP 402 even if query parameters or POST items are missing or invalid, so CDP and agents can index the path. After a PAYMENT-SIGNATURE, invalid params return HTTP 400 JSON before settlement. magent does not charge. Fix the params, then request a new 402 quote for that complete URL. Catalog misses (empty matches, found=false) are valid paid 200s. Unpaid valid requests return HTTP 402 with a base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote: retry the same PAYMENT-SIGNATURE. Full handshake and shared payment errors: Payments. Stdio MCP: /docs/mcp.

Guarantees

HTTP 402 is unpaid, including a missing query. After PAYMENT-SIGNATURE, invalid parameters return HTTP 400 before settlement. You are not charged.
exact: settlement finishes before the tool (paymentFlow upfront). batch-settlement: verify/deposit before the tool; chargedCumulativeAmount commits after HTTP 2xx. Uncertain or failed settlement fails closed (HTTP 503). Retry the same PAYMENT-SIGNATURE.
HTTP 402 is unpaid only. Do not sign a second authorization because of a 503.
Execution is timeout-bounded and concurrency-capped.
Calculator inputs are stored encrypted for allowlisted operators (Magent Console). They are not in public logs, SSH lookups, catalog, or rollups. Request logs store path without query.