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Pediatric appendicitis risk calculator (pARC)

pARC

Compute the Kharbanda 2018 Table 3 logistic probability of appendicitis from sex, age (5-18 years), pain duration, pain with walking, migration of pain to the RLQ, maximal tenderness in the RLQ, abdominal guarding, and ANC.

LIVE $0.005 USDC GET /api/calc/parc

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

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

What it computes

Compute the Kharbanda 2018 Table 3 logistic probability of appendicitis from sex, age (5-18 years), pain duration, pain with walking, migration of pain to the RLQ, maximal tenderness in the RLQ, abdominal guarding, and ANC.

When to use

When an agent already has Kharbanda 2018 Table 3 inputs and needs the published pARC probability and must not invent a PAS score, Alvarado points, an imaging order, or a nausea/vomiting term (dropped from the final model).

When not to use

• Not a medical device. Not a diagnosis and not an imaging or operating-room order. magent does not examine the child.
• Kharbanda 2018 Table 3 logistic model only. Nausea and vomiting were not significant in the final model and are not inputs.
• Age is 5-18 years (derivation). Sex-specific age terms follow Table 3: female 12-18 y and male 14-18 y are the reference; magent does not apply pARC under age 5.
• pain_duration, pain_with_walking, pain_migration_rlq, maximal_tenderness_rlq, and abdominal_guarding are caller-assigned published categories or flags. magent does not examine the abdomen.
• ANC is required in x10^3/uL. magent does not impute missing ANC from WBC. This is not the Pediatric Appendicitis Score (PAS) and not Alvarado. Kharbanda 2018 Table 4 risk strata are not returned.

Formula

L = -8.7 + 1.28*male + age_sex + pain_duration + 1.05*pain_with_walking + 0.46*pain_migration_rlq + 1.14*maximal_tenderness_rlq + 0.67*abdominal_guarding + anc (Kharbanda 2018 Table 3); age 5-7.9 y 0.38; male 5-7.9 y -1.05; age 8-13.9 y -0.72 (male 8-13.9 y and female 8-11.9 y); reference = male 14-18 y and female 12-18 y; duration lt_24 0, 24_lt_48 0.47, 48_96 0.10; ANC <14 x10^3/uL: 1.77*sqrt(ANC); ANC >=14: 6.62 instead of the sqrt term; estimated_probability = 1 / (1 + exp(-L)); estimated_probability_percent = 100 * estimated_probability

Citation

Title

Development and Validation of a Novel Pediatric Appendicitis Risk Calculator (pARC)

Authors

Kharbanda AB, Vazquez-Benitez G, Ballard DW, et al.

Source

Pediatrics. 2018;141(4):e20172699

DOI

10.1542/peds.2017-2699

Worked example

Also searched as

• pARC
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• pediatric RLQ appendicitis risk

Try

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

/api/calc/parc?age=15&sex=female&pain_duration=lt_24&pain_with_walking=false&pain_migration_rlq=false&maximal_tenderness_rlq=false&abdominal_guarding=false&anc_10e3_ul=2.0

Full URL: https://api.magentlab.com/api/calc/parc?age=15&sex=female&pain_duration=lt_24&pain_with_walking=false&pain_migration_rlq=false&maximal_tenderness_rlq=false&abdominal_guarding=false&anc_10e3_ul=2.0

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/parc?age=15&sex=female&pain_duration=lt_24&pain_with_walking=false&pain_migration_rlq=false&maximal_tenderness_rlq=false&abdominal_guarding=false&anc_10e3_ul=2.0"

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/parc 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": [
    {
      "abdominal_guarding": "false",
      "age": "15",
      "anc_10e3_ul": "2.0",
      "maximal_tenderness_rlq": "false",
      "pain_duration": "lt_24",
      "pain_migration_rlq": "false",
      "pain_with_walking": "false",
      "sex": "female"
    },
    {
      "abdominal_guarding": "false",
      "age": "15",
      "anc_10e3_ul": "2.0",
      "maximal_tenderness_rlq": "false",
      "pain_duration": "lt_24",
      "pain_migration_rlq": "false",
      "pain_with_walking": "false",
      "sex": "female"
    }
  ]
}

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/parc",
  "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": "Kharbanda AB, Vazquez-Benitez G, Ballard DW, et al.",
        "doi": "10.1542/peds.2017-2699",
        "id": "kharbanda-2018",
        "pmid": "29535251",
        "source": "Pediatrics. 2018;141(4):e20172699",
        "title": "Development and Validation of a Novel Pediatric Appendicitis Risk Calculator (pARC)"
      },
      "formula": "parc",
      "formula_expression": "L = -8.7 + 1.28*male + age_sex + pain_duration + 1.05*pain_with_walking + 0.46*pain_migration_rlq + 1.14*maximal_tenderness_rlq + 0.67*abdominal_guarding + anc (Kharbanda 2018 Table 3); age 5-7.9 y 0.38; male 5-7.9 y -1.05; age 8-13.9 y -0.72 (male 8-13.9 y and female 8-11.9 y); reference = male 14-18 y and female 12-18 y; duration lt_24 0, 24_lt_48 0.47, 48_96 0.10; ANC <14 x10^3/uL: 1.77*sqrt(ANC); ANC >=14: 6.62 instead of the sqrt term; estimated_probability = 1 / (1 + exp(-L)); estimated_probability_percent = 100 * estimated_probability",
      "age_years": 15,
      "sex": "female",
      "estimated_probability_percent": 0.2,
      "logit": -6.1968,
      "abdominal_guarding": false,
      "anc_10e3_ul": 2.0,
      "estimated_probability": 0.002032,
      "maximal_tenderness_rlq": false,
      "pain_duration": "lt_24",
      "pain_migration_rlq": false,
      "pain_with_walking": 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": "Kharbanda AB, Vazquez-Benitez G, Ballard DW, et al.",
        "doi": "10.1542/peds.2017-2699",
        "id": "kharbanda-2018",
        "pmid": "29535251",
        "source": "Pediatrics. 2018;141(4):e20172699",
        "title": "Development and Validation of a Novel Pediatric Appendicitis Risk Calculator (pARC)"
      },
      "formula": "parc",
      "formula_expression": "L = -8.7 + 1.28*male + age_sex + pain_duration + 1.05*pain_with_walking + 0.46*pain_migration_rlq + 1.14*maximal_tenderness_rlq + 0.67*abdominal_guarding + anc (Kharbanda 2018 Table 3); age 5-7.9 y 0.38; male 5-7.9 y -1.05; age 8-13.9 y -0.72 (male 8-13.9 y and female 8-11.9 y); reference = male 14-18 y and female 12-18 y; duration lt_24 0, 24_lt_48 0.47, 48_96 0.10; ANC <14 x10^3/uL: 1.77*sqrt(ANC); ANC >=14: 6.62 instead of the sqrt term; estimated_probability = 1 / (1 + exp(-L)); estimated_probability_percent = 100 * estimated_probability",
      "age_years": 15,
      "sex": "female",
      "estimated_probability_percent": 0.2,
      "logit": -6.1968,
      "abdominal_guarding": false,
      "anc_10e3_ul": 2.0,
      "estimated_probability": 0.002032,
      "maximal_tenderness_rlq": false,
      "pain_duration": "lt_24",
      "pain_migration_rlq": false,
      "pain_with_walking": false
    }
  ]
}

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": "Kharbanda AB, Vazquez-Benitez G, Ballard DW, et al.",
    "doi": "10.1542/peds.2017-2699",
    "id": "kharbanda-2018",
    "pmid": "29535251",
    "source": "Pediatrics. 2018;141(4):e20172699",
    "title": "Development and Validation of a Novel Pediatric Appendicitis Risk Calculator (pARC)"
  },
  "formula": "parc",
  "formula_expression": "L = -8.7 + 1.28*male + age_sex + pain_duration + 1.05*pain_with_walking + 0.46*pain_migration_rlq + 1.14*maximal_tenderness_rlq + 0.67*abdominal_guarding + anc (Kharbanda 2018 Table 3); age 5-7.9 y 0.38; male 5-7.9 y -1.05; age 8-13.9 y -0.72 (male 8-13.9 y and female 8-11.9 y); reference = male 14-18 y and female 12-18 y; duration lt_24 0, 24_lt_48 0.47, 48_96 0.10; ANC <14 x10^3/uL: 1.77*sqrt(ANC); ANC >=14: 6.62 instead of the sqrt term; estimated_probability = 1 / (1 + exp(-L)); estimated_probability_percent = 100 * estimated_probability",
  "age_years": 15,
  "sex": "female",
  "estimated_probability_percent": 0.2,
  "logit": -6.1968,
  "abdominal_guarding": false,
  "anc_10e3_ul": 2.0,
  "estimated_probability": 0.002032,
  "maximal_tenderness_rlq": false,
  "pain_duration": "lt_24",
  "pain_migration_rlq": false,
  "pain_with_walking": false
}

Client errors (HTTP 400)

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

Related tools

• Pediatric appendicitis score — Compute the Samuel 2002 pediatric appendicitis score from eight caller-assigned findings in children aged 4-15.
• Alvarado score — Compute the Alvarado 1986 MANTRELS score from caller-assigned findings, temperature, WBC, and neutrophil percent.

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.