Emergency · LIVE

Rule of 7s for Lyme meningitis

Rule of 7s

Apply the Cohn 2012 Rule of 7s and return whether all three published low-risk criteria hold (rule7s_low_risk).

LIVE $0.005 USDC GET /api/calc/rule_7s

Markdown: /docs/rule-7s.md · Canonical: https://magentlab.com/docs/rule-7s

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

What it computes

Apply the Cohn 2012 Rule of 7s and return whether all three published low-risk criteria hold (rule7s_low_risk).

When to use

When an agent already has headache duration in days, CSF mononuclear percent, and whether cranial-nerve palsy is present, as in Cohn 2012, and needs the published three-item Rule of 7s low-risk result. magent does not examine nerves or count CSF cells.

When not to use

• Not a medical device.
• Not a Lyme diagnosis. Low-risk on the Rule of 7s is not a diagnosis of Lyme meningitis or aseptic meningitis.
• magent does not examine nerves or count CSF cells. headache_days, csf_mononuclear_percent, and cranial_nerve_palsy are caller-assigned.
• This tool is the named three-item Rule of 7s as stated in Cohn 2012. It does not compute Avery 2006 logistic probabilities.
• Not a treatment or discharge order.

Formula

low-risk iff headache_days < 7 and csf_mononuclear_percent < 70 and cranial_nerve_palsy is false

Citation

Title

Validation of a clinical prediction rule to distinguish Lyme meningitis from aseptic meningitis

Authors

Cohn KA, Thompson AD, Shah SS, Hines EM, Lyons TW, Welsh EJ, Nigrovic LE

Source

Pediatrics. 2012;129(1):e46-e53

DOI

10.1542/peds.2011-1215

Worked example

Also searched as

• Rule of 7s
• Rule of 7's
• Cohn Rule of 7s
• Lyme meningitis rule
• Lyme vs aseptic meningitis
• Cohn 2012
• Rule of sevens

Try

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

/api/calc/rule_7s?headache_days=3&csf_mononuclear_percent=40&cranial_nerve_palsy=false

Full URL: https://api.magentlab.com/api/calc/rule_7s?headache_days=3&csf_mononuclear_percent=40&cranial_nerve_palsy=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/rule_7s?headache_days=3&csf_mononuclear_percent=40&cranial_nerve_palsy=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/rule_7s 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": [
    {
      "cranial_nerve_palsy": "false",
      "csf_mononuclear_percent": "40",
      "headache_days": "3"
    },
    {
      "cranial_nerve_palsy": "false",
      "csf_mononuclear_percent": "40",
      "headache_days": "3"
    }
  ]
}

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/rule_7s",
  "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": "Cohn KA, Thompson AD, Shah SS, Hines EM, Lyons TW, Welsh EJ, Nigrovic LE",
        "doi": "10.1542/peds.2011-1215",
        "id": "cohn-2012",
        "pmid": "22184646",
        "source": "Pediatrics. 2012;129(1):e46-e53",
        "title": "Validation of a clinical prediction rule to distinguish Lyme meningitis from aseptic meningitis"
      },
      "formula": "rule_7s",
      "formula_expression": "low-risk iff headache_days < 7 and csf_mononuclear_percent < 70 and cranial_nerve_palsy is false",
      "criteria": [
        {
          "value": 3,
          "factor": "headache_days_lt_7",
          "met": true
        },
        {
          "value": 40.0,
          "factor": "csf_mononuclear_percent_lt_70",
          "met": true
        },
        {
          "factor": "no_cranial_nerve_palsy",
          "met": true
        }
      ],
      "rule7s_low_risk": 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": "Cohn KA, Thompson AD, Shah SS, Hines EM, Lyons TW, Welsh EJ, Nigrovic LE",
        "doi": "10.1542/peds.2011-1215",
        "id": "cohn-2012",
        "pmid": "22184646",
        "source": "Pediatrics. 2012;129(1):e46-e53",
        "title": "Validation of a clinical prediction rule to distinguish Lyme meningitis from aseptic meningitis"
      },
      "formula": "rule_7s",
      "formula_expression": "low-risk iff headache_days < 7 and csf_mononuclear_percent < 70 and cranial_nerve_palsy is false",
      "criteria": [
        {
          "value": 3,
          "factor": "headache_days_lt_7",
          "met": true
        },
        {
          "value": 40.0,
          "factor": "csf_mononuclear_percent_lt_70",
          "met": true
        },
        {
          "factor": "no_cranial_nerve_palsy",
          "met": true
        }
      ],
      "rule7s_low_risk": 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": "Cohn KA, Thompson AD, Shah SS, Hines EM, Lyons TW, Welsh EJ, Nigrovic LE",
    "doi": "10.1542/peds.2011-1215",
    "id": "cohn-2012",
    "pmid": "22184646",
    "source": "Pediatrics. 2012;129(1):e46-e53",
    "title": "Validation of a clinical prediction rule to distinguish Lyme meningitis from aseptic meningitis"
  },
  "formula": "rule_7s",
  "formula_expression": "low-risk iff headache_days < 7 and csf_mononuclear_percent < 70 and cranial_nerve_palsy is false",
  "criteria": [
    {
      "value": 3,
      "factor": "headache_days_lt_7",
      "met": true
    },
    {
      "value": 40.0,
      "factor": "csf_mononuclear_percent_lt_70",
      "met": true
    },
    {
      "factor": "no_cranial_nerve_palsy",
      "met": true
    }
  ],
  "rule7s_low_risk": true
}

Client errors (HTTP 400)

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

Related tools

• Bacterial Meningitis Score — Sum the Nigrovic 2002 Bacterial Meningitis Score weights for children with CSF pleocytosis and return very_low_risk (0) or not_low_risk (≥1).

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.