Infection / VTE · LIVE

Altitude-adjusted PERC

Apply the Madsen 2019 altitude-adjusted eight-factor pulmonary embolism rule-out criteria (hypoxia as O2 sat <90% at ~4980 ft) and return whether all eight are met (PERC-negative).

LIVE $0.005 USDC GET /api/calc/perc_altitude

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

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

What it computes

Apply the Madsen 2019 altitude-adjusted eight-factor pulmonary embolism rule-out criteria (hypoxia as O2 sat <90% at ~4980 ft) 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 Kline, and the encounter is at altitude as studied by Madsen (chest pain and/or SOB at ~4980 ft), and needs a published altitude-adjusted PERC-negative result from caller-assigned findings.

When not to use

• Not a medical device.
• Not a PE diagnosis and not sea-level PERC (that is perc). Not a D-dimer protocol.
• Only for patients who already have a low pretest probability of pulmonary embolism, as in Kline. Madsen studied chest pain and/or SOB at altitude. magent does not assign pretest probability.
• The caller assigns age, pulse, SaO2, and the five clinical flags. magent does not measure vitals or examine the patient.

Formula

PERC-negative iff age < 50 and pulse < 100 bpm and SaO2 ≥ 90% 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

Impact of altitude-adjusted hypoxia on the Pulmonary Embolism Rule-out Criteria.

Authors

Madsen T, Jedick R, Teeples T, Carlson M, Steenblik J

Source

Am J Emerg Med. 2019;37(2):281-285 (Epub 2018 May 24)

DOI

10.1016/j.ajem.2018.05.050

Worked example

Also searched as

• altitude-adjusted PERC
• Madsen PERC
• PERC altitude
• altitude PERC rule
• hypoxia-adjusted PERC
• PERC 4980 ft
• altitude-adjusted pulmonary embolism rule-out

Try

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

/api/calc/perc_altitude?age=40&heart_rate_bpm=80&spo2_percent=90&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_altitude?age=40&heart_rate_bpm=80&spo2_percent=90&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_altitude?age=40&heart_rate_bpm=80&spo2_percent=90&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. The first item is the GET unit; each additional item is $0.002. Invalid items return HTTP 400 before settlement.

POST /api/calc/perc_altitude 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": [
    {
      "age": "40",
      "estrogen_use": "false",
      "heart_rate_bpm": "80",
      "hemoptysis": "false",
      "prior_vte": "false",
      "recent_surgery_or_trauma": "false",
      "spo2_percent": "90",
      "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": "90",
      "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_altitude",
  "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": "Madsen T, Jedick R, Teeples T, Carlson M, Steenblik J",
        "doi": "10.1016/j.ajem.2018.05.050",
        "id": "madsen-2019",
        "pmid": "29848460",
        "source": "Am J Emerg Med. 2019;37(2):281-285 (Epub 2018 May 24)",
        "title": "Impact of altitude-adjusted hypoxia on the Pulmonary Embolism Rule-out Criteria."
      },
      "formula": "perc_altitude",
      "formula_expression": "PERC-negative iff age < 50 and pulse < 100 bpm and SaO2 ≥ 90% 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": 90.0,
          "factor": "sao2_ge_90",
          "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": "Madsen T, Jedick R, Teeples T, Carlson M, Steenblik J",
        "doi": "10.1016/j.ajem.2018.05.050",
        "id": "madsen-2019",
        "pmid": "29848460",
        "source": "Am J Emerg Med. 2019;37(2):281-285 (Epub 2018 May 24)",
        "title": "Impact of altitude-adjusted hypoxia on the Pulmonary Embolism Rule-out Criteria."
      },
      "formula": "perc_altitude",
      "formula_expression": "PERC-negative iff age < 50 and pulse < 100 bpm and SaO2 ≥ 90% 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": 90.0,
          "factor": "sao2_ge_90",
          "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": "Madsen T, Jedick R, Teeples T, Carlson M, Steenblik J",
    "doi": "10.1016/j.ajem.2018.05.050",
    "id": "madsen-2019",
    "pmid": "29848460",
    "source": "Am J Emerg Med. 2019;37(2):281-285 (Epub 2018 May 24)",
    "title": "Impact of altitude-adjusted hypoxia on the Pulmonary Embolism Rule-out Criteria."
  },
  "formula": "perc_altitude",
  "formula_expression": "PERC-negative iff age < 50 and pulse < 100 bpm and SaO2 ≥ 90% 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": 90.0,
      "factor": "sao2_ge_90",
      "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

• PERC rule — Apply the Kline 2004 eight-factor pulmonary embolism rule-out criteria and return whether all eight are met (PERC-negative).
• Wells PE — Compute the Wells pulmonary-embolism probability score and return three-tier and two-tier bands.

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. HTTP 402 never includes the tool JSON.
• 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.