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PERC rule

Apply the Kline 2004 eight-factor pulmonary embolism rule-out criteria and return whether all eight are met (PERC-negative).

Also searched as

• PERC rule
• pulmonary embolism rule-out criteria
• Kline PERC
• PE rule-out criteria
• PERC negative
• pulmonary embolism block rule

LIVE $0.005 USDC GET /api/calc/perc

Markdown: /docs/perc.md · Canonical: https://magentlab.com/docs/perc

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

What it computes

Apply the Kline 2004 eight-factor pulmonary embolism rule-out criteria and return whether all eight are met (PERC-negative).

When to use

When an agent already has a low pretest probability of PE, as in the derivation paper, and needs a published PERC-negative result from caller-assigned findings.

When not to use

• Not a diagnosis and not a D-dimer protocol.
• Only for patients who already have a low pretest probability of pulmonary embolism, as in the derivation paper. magent does not assign pretest probability.
• The caller assigns age, pulse, SaO2, and the five clinical flags. magent does not examine the patient.
• This tool is the Kline 2004 derivation rule. Altitude-adjusted PERC is not this tool.

Formula

PERC-negative iff age < 50 and pulse < 100 bpm and SaO2 > 94% and no unilateral leg swelling and no hemoptysis and no recent trauma or surgery and no prior PE or DVT and no hormone use

Citation

Title

Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism

Authors

Kline JA, Mitchell AM, Kabrhel C, Richman PB, Courtney DM

Source

J Thromb Haemost. 2004;2(8):1247-1255

DOI

10.1111/j.1538-7836.2004.00790.x

Worked example

Try

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

/api/calc/perc?age=40&heart_rate_bpm=80&spo2_percent=98&unilateral_leg_swelling=false&hemoptysis=false&recent_surgery_or_trauma=false&prior_vte=false&estrogen_use=false

Full URL: https://api.magentlab.com/api/calc/perc?age=40&heart_rate_bpm=80&spo2_percent=98&unilateral_leg_swelling=false&hemoptysis=false&recent_surgery_or_trauma=false&prior_vte=false&estrogen_use=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/perc?age=40&heart_rate_bpm=80&spo2_percent=98&unilateral_leg_swelling=false&hemoptysis=false&recent_surgery_or_trauma=false&prior_vte=false&estrogen_use=false"

Parameters

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.

POST /api/calc/perc Max 25 unit_amount * n 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 (fixture)

{
  "items": [
    {
      "age": "40",
      "estrogen_use": "false",
      "heart_rate_bpm": "80",
      "hemoptysis": "false",
      "prior_vte": "false",
      "recent_surgery_or_trauma": "false",
      "spo2_percent": "98",
      "unilateral_leg_swelling": "false"
    },
    {
      "age": "40",
      "estrogen_use": "false",
      "heart_rate_bpm": "80",
      "hemoptysis": "false",
      "prior_vte": "false",
      "recent_surgery_or_trauma": "false",
      "spo2_percent": "98",
      "unilateral_leg_swelling": "false"
    }
  ]
}

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/perc",
  "items": [
    {
      "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": "Kline JA, Mitchell AM, Kabrhel C, Richman PB, Courtney DM",
        "doi": "10.1111/j.1538-7836.2004.00790.x",
        "id": "kline-2004",
        "source": "J Thromb Haemost. 2004;2(8):1247-1255",
        "title": "Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism"
      },
      "formula": "perc",
      "formula_expression": "PERC-negative iff age < 50 and pulse < 100 bpm and SaO2 > 94% and no unilateral leg swelling and no hemoptysis and no recent trauma or surgery and no prior PE or DVT and no hormone use",
      "criteria": [
        {
          "value": 40,
          "factor": "age_lt_50",
          "met": true
        },
        {
          "value": 80,
          "factor": "pulse_lt_100",
          "met": true
        },
        {
          "value": 98.0,
          "factor": "sao2_gt_94",
          "met": true
        },
        {
          "factor": "no_unilateral_leg_swelling",
          "met": true
        },
        {
          "factor": "no_hemoptysis",
          "met": true
        },
        {
          "factor": "no_recent_surgery_or_trauma",
          "met": true
        },
        {
          "factor": "no_prior_vte",
          "met": true
        },
        {
          "factor": "no_estrogen_use",
          "met": true
        }
      ],
      "perc_negative": true
    },
    {
      "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": "Kline JA, Mitchell AM, Kabrhel C, Richman PB, Courtney DM",
        "doi": "10.1111/j.1538-7836.2004.00790.x",
        "id": "kline-2004",
        "source": "J Thromb Haemost. 2004;2(8):1247-1255",
        "title": "Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism"
      },
      "formula": "perc",
      "formula_expression": "PERC-negative iff age < 50 and pulse < 100 bpm and SaO2 > 94% and no unilateral leg swelling and no hemoptysis and no recent trauma or surgery and no prior PE or DVT and no hormone use",
      "criteria": [
        {
          "value": 40,
          "factor": "age_lt_50",
          "met": true
        },
        {
          "value": 80,
          "factor": "pulse_lt_100",
          "met": true
        },
        {
          "value": 98.0,
          "factor": "sao2_gt_94",
          "met": true
        },
        {
          "factor": "no_unilateral_leg_swelling",
          "met": true
        },
        {
          "factor": "no_hemoptysis",
          "met": true
        },
        {
          "factor": "no_recent_surgery_or_trauma",
          "met": true
        },
        {
          "factor": "no_prior_vte",
          "met": true
        },
        {
          "factor": "no_estrogen_use",
          "met": true
        }
      ],
      "perc_negative": true
    }
  ]
}

Response

Example JSON

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

{
  "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": "Kline JA, Mitchell AM, Kabrhel C, Richman PB, Courtney DM",
    "doi": "10.1111/j.1538-7836.2004.00790.x",
    "id": "kline-2004",
    "source": "J Thromb Haemost. 2004;2(8):1247-1255",
    "title": "Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism"
  },
  "formula": "perc",
  "formula_expression": "PERC-negative iff age < 50 and pulse < 100 bpm and SaO2 > 94% and no unilateral leg swelling and no hemoptysis and no recent trauma or surgery and no prior PE or DVT and no hormone use",
  "criteria": [
    {
      "value": 40,
      "factor": "age_lt_50",
      "met": true
    },
    {
      "value": 80,
      "factor": "pulse_lt_100",
      "met": true
    },
    {
      "value": 98.0,
      "factor": "sao2_gt_94",
      "met": true
    },
    {
      "factor": "no_unilateral_leg_swelling",
      "met": true
    },
    {
      "factor": "no_hemoptysis",
      "met": true
    },
    {
      "factor": "no_recent_surgery_or_trauma",
      "met": true
    },
    {
      "factor": "no_prior_vte",
      "met": true
    },
    {
      "factor": "no_estrogen_use",
      "met": true
    }
  ],
  "perc_negative": true
}

Client errors (HTTP 400)

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

Related tools

• Wells PE — Compute the Wells pulmonary-embolism probability score and return three-tier and two-tier bands.

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. 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

• 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.