# PERC rule PERC rule ## Also searched as - PERC rule - pulmonary embolism rule-out criteria - Kline PERC - PE rule-out criteria - PERC negative - pulmonary embolism block rule Status: LIVE Price: $0.005 USDC `GET /api/calc/perc` HTML: https://magentlab.com/docs/perc Markdown: https://magentlab.com/docs/perc.md 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 [Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism](https://doi.org/10.1111/j.1538-7836.2004.00790.x) Kline JA, Mitchell AM, Kabrhel C, Richman PB, Courtney DM J Thromb Haemost. 2004;2(8):1247-1255 DOI: [10.1111/j.1538-7836.2004.00790.x](https://doi.org/10.1111/j.1538-7836.2004.00790.x) ## Worked example ### All eight criteria met Given: `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` 1. Age 40 < 50; pulse 80 < 100; SaO2 98 > 94 2. Five harmful findings absent 3. PERC-negative ### Age 50 fails the age criterion Given: `age=50, estrogen_use=false, heart_rate_bpm=80, hemoptysis=false, prior_vte=false, recent_surgery_or_trauma=false, spo2_percent=98, unilateral_leg_swelling=false` 1. Age 50 is not < 50 2. PERC-negative is false ## Parameters - `age` (integer, required): Age in years (18-120). Criterion met when age < 50; 50 does not meet. - `heart_rate_bpm` (integer, required): Pulse in beats per minute (integer 30-220). Criterion met when pulse < 100; 100 does not meet. - `spo2_percent` (number, required): Oxygen saturation percent (50-100). Criterion met when SaO2 > 94; 94 does not meet. - `unilateral_leg_swelling` (boolean, required): Unilateral leg swelling. true or false as assigned by the caller. Criterion met when false. - `hemoptysis` (boolean, required): Hemoptysis. true or false as assigned by the caller. Criterion met when false. - `recent_surgery_or_trauma` (boolean, required): Recent trauma or surgery. true or false as assigned by the caller. Criterion met when false. - `prior_vte` (boolean, required): Prior PE or DVT. true or false as assigned by the caller. Criterion met when false. - `estrogen_use` (boolean, required): Hormone or exogenous estrogen use. true or false as assigned by the caller. Criterion met when false. ## 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/perc` 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": "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" } ] } ``` Human paywall (two-item fixture): https://api.magentlab.com/paywall/bulk/perc Example 200: ```json { "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 fields - `formula` (string): perc - `formula_expression` (string): Eight Kline 2004 criteria - `perc_negative` (boolean): true only when all eight criteria are met. Not a diagnosis. - `criteria` (array): Per-factor rows with factor, met, and value when numeric - `citation` (object): Kline 2004 J Thromb Haemost citation - `disclaimer` (string): Not-a-device notice ## Example JSON Frozen fixture. Not a live lookup. ```json { "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 } ``` ## Errors - HTTP 400 `invalid_age`: age must be an integer from 18 to 120 Returned before settlement; you are not charged. - HTTP 400 `invalid_heart_rate`: heart_rate_bpm must be an integer from 30 to 220 Returned before settlement; you are not charged. - HTTP 400 `invalid_spo2`: spo2_percent must be a number from 50 to 100. 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 - [Wells PE](https://magentlab.com/docs/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. - 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 n times the GET unit. 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.