# CRB-65 community-acquired pneumonia

CRB-65

Status: LIVE
Price: $0.005 USDC
`GET /api/calc/crb65`
HTML: https://magentlab.com/docs/crb-65
Markdown: https://magentlab.com/docs/crb-65.md

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

## What it computes

Compute the Lim 2003 CRB-65 community-acquired pneumonia score from age and caller-assigned confusion, respiratory-rate, and blood-pressure flags. Urea is not an input.

## When to use

When an agent needs the published CRB-65 total (no urea) and must not substitute CURB-65 or invent site-of-care advice.

## When not to use

- Not a diagnosis and not a site-of-care decision.
- This is CRB-65 (no urea), not CURB-65. magent does not convert BUN.
- The caller assigns confusion, respiratory_rate_ge_30, and low_blood_pressure flags the same way as CURB-65.

## Formula

```
CRB-65 = confusion + respiratory_rate_ge_30 + low_blood_pressure + age_ge_65; max 4
```

## Citation

[Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study](https://doi.org/10.1136/thorax.58.5.377)
Lim WS, van der Eerden MM, Laing R, et al.
Thorax. 2003;58(5):377-382
DOI: [10.1136/thorax.58.5.377](https://doi.org/10.1136/thorax.58.5.377)

## Worked example

### Age 40, all flags false

Given: `age=40, confusion=false, low_blood_pressure=false, respiratory_rate_ge_30=false`

1. Confusion false → 0; respiratory_rate_ge_30 false → 0; low_blood_pressure false → 0; age 40 is not ≥65 → 0
2. Score = 0 (max 4)


### Age 70 and confusion

Given: `age=70, confusion=true, low_blood_pressure=false, respiratory_rate_ge_30=false`

1. Confusion → 1; age ≥65 → 1
2. Score = 2 (max 4)


## Also searched as

- CRB 65
- CRB65
- CRB-65 score
- Lim CRB-65
- CAP CRB-65

## Parameters

- `age` (integer, required): Age in years (18-120). Age ≥65 scores 1.
- `confusion` (boolean, required): New confusion (C) as assigned by the caller. true or false.
- `respiratory_rate_ge_30` (boolean, required): Respiratory rate ≥30/min (R) as assigned by the caller. true or false.
- `low_blood_pressure` (boolean, required): SBP <90 mmHg or DBP ≤60 mmHg (B) as assigned by the caller. true or false. magent does not take BP numbers.

## 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.

Method: `POST /api/calc/crb65`
Max items: 25
Price: unit_amount + extra_item_amount * (n - 1) (unit 5000 atomic, extra 2000 atomic)
Status: 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:

```json
{
  "items": [
    {
      "age": "40",
      "confusion": "false",
      "low_blood_pressure": "false",
      "respiratory_rate_ge_30": "false"
    },
    {
      "age": "40",
      "confusion": "false",
      "low_blood_pressure": "false",
      "respiratory_rate_ge_30": "false"
    }
  ]
}
```

Human paywall (two-item fixture): https://api.magentlab.com/paywall/bulk/crb-65

Example 200:

```json
{
  "count": 2,
  "path": "/api/calc/crb65",
  "items": [
    {
      "components": [
        {
          "factor": "confusion",
          "points": 0,
          "present": false
        },
        {
          "factor": "respiratory_rate_ge_30",
          "points": 0,
          "present": false
        },
        {
          "factor": "low_blood_pressure",
          "points": 0,
          "present": false
        },
        {
          "value": 40,
          "factor": "age_ge_65",
          "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": "Lim WS, van der Eerden MM, Laing R, et al.",
        "doi": "10.1136/thorax.58.5.377",
        "id": "lim-2003",
        "source": "Thorax. 2003;58(5):377-382",
        "title": "Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study"
      },
      "formula": "crb65",
      "formula_expression": "CRB-65 = confusion + respiratory_rate_ge_30 + low_blood_pressure + age_ge_65; max 4",
      "age_years": 40,
      "max_score": 4,
      "score": 0
    },
    {
      "components": [
        {
          "factor": "confusion",
          "points": 0,
          "present": false
        },
        {
          "factor": "respiratory_rate_ge_30",
          "points": 0,
          "present": false
        },
        {
          "factor": "low_blood_pressure",
          "points": 0,
          "present": false
        },
        {
          "value": 40,
          "factor": "age_ge_65",
          "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": "Lim WS, van der Eerden MM, Laing R, et al.",
        "doi": "10.1136/thorax.58.5.377",
        "id": "lim-2003",
        "source": "Thorax. 2003;58(5):377-382",
        "title": "Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study"
      },
      "formula": "crb65",
      "formula_expression": "CRB-65 = confusion + respiratory_rate_ge_30 + low_blood_pressure + age_ge_65; max 4",
      "age_years": 40,
      "max_score": 4,
      "score": 0
    }
  ]
}
```

## Response fields

- `formula` (string): crb65
- `formula_expression` (string): Exact expression used
- `score` (integer): Total points 0-4
- `max_score` (integer): Always 4
- `age_years` (integer): Age used for the 65 criterion
- `components` (array): Per-factor points
- `citation` (object): Thorax 2003 citation
- `disclaimer` (string): Not-a-device notice

## Example JSON

Frozen fixture. Not a live lookup.

```json
{
  "components": [
    {
      "factor": "confusion",
      "points": 0,
      "present": false
    },
    {
      "factor": "respiratory_rate_ge_30",
      "points": 0,
      "present": false
    },
    {
      "factor": "low_blood_pressure",
      "points": 0,
      "present": false
    },
    {
      "value": 40,
      "factor": "age_ge_65",
      "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": "Lim WS, van der Eerden MM, Laing R, et al.",
    "doi": "10.1136/thorax.58.5.377",
    "id": "lim-2003",
    "source": "Thorax. 2003;58(5):377-382",
    "title": "Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study"
  },
  "formula": "crb65",
  "formula_expression": "CRB-65 = confusion + respiratory_rate_ge_30 + low_blood_pressure + age_ge_65; max 4",
  "age_years": 40,
  "max_score": 4,
  "score": 0
}
```

## 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.

Shared HTTP 402 and 503: https://magentlab.com/docs/payments

## Related tools

- [CURB-65](https://magentlab.com/docs/curb65) — Compute the CURB-65 community-acquired pneumonia severity score from age and discrete flags.

## 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.

- GET the tool with Accept: application/json (do not send Accept: text/html unless you want the human paywall).
- HTTP 402 means you have not paid. Decode the base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote.
- Sign EIP-3009 (scheme exact, assetTransferMethod eip3009) with validBefore = now + accepts[0].maxTimeoutSeconds (600 seconds). That window starts when you sign and must cover wallet confirmation plus CDP verify and settle. Magent retries transient facilitator 429/5xx before answering. Do not send upto or batch-settlement payloads; magent does not offer those schemes.
- Retry the same URL with PAYMENT-SIGNATURE (base64 JSON echoing accepted, payload, and extensions when present).
- Success is HTTP 200 JSON plus PAYMENT-RESPONSE. Settlement happens before the tool runs. HTTP 503 settlement_uncertain or settle_failed: retry the same PAYMENT-SIGNATURE. Mint a new nonce only after a new HTTP 402.

- offered `exact` on eip155:8453: Fixed-price USDC on Base. The buyer authorizes the advertised amount (EIP-3009). magent settles before the tool runs (paymentFlow upfront). extra.assetTransferMethod=eip3009 extra.paymentFlow=upfront.

- not offered `upto`: Not offered. Usage-based: buyer authorizes a ceiling, seller settles the actual amount after work. Reserved for a future metered tool. Not for current calculators or code search.
- not offered `batch-settlement`: Not offered. Payment-channel vouchers claimed later in batches. Not the same as POST {items} bulk (that is still exact).

Same-path POST {items} is still scheme exact: one EIP-3009 authorization for GET unit plus $0.002 per extra item. That is not x402 batch-settlement (payment channels / vouchers).

Shared HTTP 402 and 503 table: https://magentlab.com/docs/payments

Stdio MCP (one process per host): https://magentlab.com/docs/mcp

## Guarantees

- Invalid query parameters return HTTP 400 before settlement. You are not charged.
- Settlement finishes before the tool executes (paymentFlow upfront). 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.