# CHADS2

Status: WEDGE
Price: $0.005 USDC
`GET /api/calc/chads2`
HTML: https://magentlab.com/docs/chads2
Markdown: https://magentlab.com/docs/chads2.md

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

## What it computes

Compute the CHADS2 stroke-risk score from discrete clinical flags.

## When to use

When an agent needs the 2001 Gage CHADS2 total and must not invent points from a chart narrative.

## When not to use

- Not a diagnosis and not an anticoagulation order or treatment recommendation.
- CHA2DS2-VASc superseded CHADS2 for many guidelines; magent still ships the 2001 score as published.
- Flags are caller-supplied booleans. magent does not infer CHF or stroke history from text.

## Formula

```
CHADS2 = CHF 1 + hypertension 1 + age≥75 1 + diabetes 1 + stroke/TIA 2; max 6
```

## Citation

Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation
Gage BF, Waterman AD, Shannon W, Boechler M, Rich MW, Radford MJ
JAMA. 2001;285(22):2864-2870
DOI: [10.1001/jama.285.22.2864](https://doi.org/10.1001/jama.285.22.2864)

## Worked example

### Age 78, HTN + diabetes

Given: `age=78, chf=false, diabetes=true, hypertension=true, stroke_tia=false`

1. Age ≥75 → 1; hypertension → 1; diabetes → 1
2. Score = 3


## Parameters

- `age` (integer, required): Age in years (18-120). ≥75 scores 1.
- `chf` (boolean, required): Congestive heart failure or LV dysfunction. true or false.
- `hypertension` (boolean, required): Hypertension history. true or false.
- `diabetes` (boolean, required): Diabetes mellitus. true or false.
- `stroke_tia` (boolean, required): Prior stroke or TIA. true or false (2 points).

## Bulk (POST)

POST the same path with a JSON items array. Price is n times the GET unit. Invalid items return HTTP 400 before settlement.

Method: `POST /api/calc/chads2`
Max items: 25
Price: unit_amount * n (unit 5000 atomic)
Status: PREVIEW

- 1 to 25 items. Each item uses the same keys as the GET query parameters.
- 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:

```json
{
  "items": [
    {
      "age": "78",
      "chf": "false",
      "diabetes": "true",
      "hypertension": "true",
      "stroke_tia": "false"
    },
    {
      "age": "78",
      "chf": "false",
      "diabetes": "true",
      "hypertension": "true",
      "stroke_tia": "false"
    }
  ]
}
```

Human paywall (two-item fixture): https://api.magentlab.com/paywall/bulk/chads2

Example 200:

```json
{
  "count": 2,
  "path": "/api/calc/chads2",
  "items": [
    {
      "components": [
        {
          "factor": "congestive_heart_failure",
          "points": 0,
          "present": false
        },
        {
          "factor": "hypertension",
          "points": 1,
          "present": true
        },
        {
          "value": 78,
          "factor": "age_ge_75",
          "points": 1,
          "present": true
        },
        {
          "factor": "diabetes",
          "points": 1,
          "present": true
        },
        {
          "factor": "stroke_tia",
          "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": "Gage BF, Waterman AD, Shannon W, Boechler M, Rich MW, Radford MJ",
        "doi": "10.1001/jama.285.22.2864",
        "id": "gage-2001",
        "source": "JAMA. 2001;285(22):2864-2870",
        "title": "Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation"
      },
      "formula": "chads2",
      "formula_expression": "CHADS2 = CHF 1 + hypertension 1 + age≥75 1 + diabetes 1 + stroke/TIA 2; max 6",
      "age_years": 78,
      "max_score": 6,
      "score": 3
    },
    {
      "components": [
        {
          "factor": "congestive_heart_failure",
          "points": 0,
          "present": false
        },
        {
          "factor": "hypertension",
          "points": 1,
          "present": true
        },
        {
          "value": 78,
          "factor": "age_ge_75",
          "points": 1,
          "present": true
        },
        {
          "factor": "diabetes",
          "points": 1,
          "present": true
        },
        {
          "factor": "stroke_tia",
          "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": "Gage BF, Waterman AD, Shannon W, Boechler M, Rich MW, Radford MJ",
        "doi": "10.1001/jama.285.22.2864",
        "id": "gage-2001",
        "source": "JAMA. 2001;285(22):2864-2870",
        "title": "Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation"
      },
      "formula": "chads2",
      "formula_expression": "CHADS2 = CHF 1 + hypertension 1 + age≥75 1 + diabetes 1 + stroke/TIA 2; max 6",
      "age_years": 78,
      "max_score": 6,
      "score": 3
    }
  ]
}
```

## Response fields

- `formula` (string): chads2
- `formula_expression` (string): Exact expression used
- `score` (integer): Total points 0-6
- `max_score` (integer): Always 6
- `age_years` (integer): Age used for the ≥75 criterion
- `components` (array): Per-factor points
- `citation` (object): JAMA 2001 citation
- `disclaimer` (string): Not-a-device notice

## Example JSON

Frozen fixture. Not a live lookup.

```json
{
  "components": [
    {
      "factor": "congestive_heart_failure",
      "points": 0,
      "present": false
    },
    {
      "factor": "hypertension",
      "points": 1,
      "present": true
    },
    {
      "value": 78,
      "factor": "age_ge_75",
      "points": 1,
      "present": true
    },
    {
      "factor": "diabetes",
      "points": 1,
      "present": true
    },
    {
      "factor": "stroke_tia",
      "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": "Gage BF, Waterman AD, Shannon W, Boechler M, Rich MW, Radford MJ",
    "doi": "10.1001/jama.285.22.2864",
    "id": "gage-2001",
    "source": "JAMA. 2001;285(22):2864-2870",
    "title": "Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation"
  },
  "formula": "chads2",
  "formula_expression": "CHADS2 = CHF 1 + hypertension 1 + age≥75 1 + diabetes 1 + stroke/TIA 2; max 6",
  "age_years": 78,
  "max_score": 6,
  "score": 3
}
```

## Errors

- HTTP 400 `invalid_age`: age must be an integer from 18 to 120 Returned before settlement; you are not charged.
- HTTP 400 `invalid_flag`: boolean clinical flags must be true or false Returned before settlement; you are not charged.
- HTTP 400 `invalid_items`: POST body must be a JSON object with only an items array Returned before settlement; you are not charged.
- HTTP 400 `invalid_item_count`: items must be an array of 1 to 25 objects Returned before settlement; you are not charged.
- HTTP 400 `invalid_item`: each items entry must be a JSON object Returned before settlement; you are not charged.
- HTTP 402 `payment_required`: Missing or invalid PAYMENT-SIGNATURE; decode the PAYMENT-REQUIRED header
- HTTP 409 `payment_in_progress`: The same authorization nonce is already being settled; retry shortly
- HTTP 429 `rate_limited`: Too many requests from this client
- HTTP 503 `settlement_uncertain`: Settlement is unconfirmed; retry with the same PAYMENT-SIGNATURE
- HTTP 503 `facilitator_unavailable`: Payment facilitator unavailable
- HTTP 503 `facilitator_misconfigured`: Payment facilitator is not configured
- HTTP 503 `facilitator_unauthorized`: Payment facilitator rejected credentials
- HTTP 503 `ledger_unavailable`: Payment ledger unavailable
- HTTP 503 `payment_unavailable`: Payment processing unavailable

## Related tools

- [CHA2DS2-VASc](https://magentlab.com/docs/cha2ds2-vasc) — Compute the CHA2DS2-VASc stroke-risk score from discrete clinical flags.

## Also searched as

- CHADS2
- CHADS₂
- Gage 2001 score
- AF stroke score

## Payment

Required query parameters must be present and valid. 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.

## Guarantees

- Invalid query parameters return HTTP 400 before settlement. You are not charged.
- Settlement finishes before the tool executes. Uncertain settlement fails closed (HTTP 503).
- Execution is timeout-bounded and concurrency-capped.
- Calculator inputs are not persisted. Request logs store path without query.