Emergency · LIVE

San Francisco Syncope Rule

Compute the San Francisco Syncope Rule (CHESS) criterion count and rule-positive flag from published cutoffs.

LIVE $0.005 USDC GET /api/calc/sf_syncope

Markdown: /docs/sf-syncope.md · Canonical: https://magentlab.com/docs/sf-syncope

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

What it computes

Compute the San Francisco Syncope Rule (CHESS) criterion count and rule-positive flag from published cutoffs.

When to use

When an agent needs the published CHESS arithmetic and must not invent a disposition from a syncope narrative.

When not to use

Not a disposition protocol. Rule-positive means any CHESS criterion, not a diagnosis.
Derivation cohort was emergency-department syncope. magent applies the published hematocrit <30% and SBP <90 mm Hg cutoffs; it does not interpret an ECG.

Formula

CHESS = chf + hematocrit_lt_30 + abnormal_ecg + shortness_of_breath + systolic_bp_lt_90; rule-positive if score ≥ 1; max 5

Citation

Title: Derivation of the San Francisco Syncope Rule to predict patients with short-term serious outcomes
Authors: Quinn JV, Stiell IG, McDermott DA, Sellers KL, Kohn MA, Wells GA
Source: Ann Emerg Med. 2004;43(2):224-232
DOI: 10.1016/S0196-0644(03)00823-0

Worked example

All CHESS criteria negative

Given: abnormal_ecg=falsechf=falsehematocrit_percent=40shortness_of_breath=falsesystolic_bp_mm_hg=120

CHF absent; hematocrit 40% (≥30); ECG not abnormal; no dyspnea; SBP 120 (≥90)
Score = 0; rule-positive false

Also searched as

San Francisco Syncope Rule
SFSR
CHESS syncope
Quinn syncope rule

Try

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

/api/calc/sf_syncope?chf=false&hematocrit_percent=40&abnormal_ecg=false&shortness_of_breath=false&systolic_bp_mm_hg=120

Full URL: https://api.magentlab.com/api/calc/sf_syncope?chf=false&hematocrit_percent=40&abnormal_ecg=false&shortness_of_breath=false&systolic_bp_mm_hg=120

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/sf_syncope?chf=false&hematocrit_percent=40&abnormal_ecg=false&shortness_of_breath=false&systolic_bp_mm_hg=120"

Parameters

Name	Type	Required	Description
`chf`	boolean	required	History of congestive heart failure (C). true or false.
`hematocrit_percent`	number	required	Hematocrit in percent (10-70). Scores 1 when <30; 30 is negative.
`abnormal_ecg`	boolean	required	Abnormal ECG (E). true or false. Caller-assigned; magent does not read tracings.
`shortness_of_breath`	boolean	required	Shortness of breath (S). true or false.
`systolic_bp_mm_hg`	number	required	Systolic BP in mm Hg (50-250). Scores 1 when <90; 90 is negative.

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/sf_syncope 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": [
    {
      "abnormal_ecg": "false",
      "chf": "false",
      "hematocrit_percent": "40",
      "shortness_of_breath": "false",
      "systolic_bp_mm_hg": "120"
    },
    {
      "abnormal_ecg": "false",
      "chf": "false",
      "hematocrit_percent": "40",
      "shortness_of_breath": "false",
      "systolic_bp_mm_hg": "120"
    }
  ]
}

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/sf_syncope",
  "items": [
    {
      "components": [
        {
          "factor": "chf",
          "points": 0,
          "present": false
        },
        {
          "value": 40.0,
          "factor": "hematocrit_lt_30",
          "points": 0,
          "present": false
        },
        {
          "factor": "abnormal_ecg",
          "points": 0,
          "present": false
        },
        {
          "factor": "shortness_of_breath",
          "points": 0,
          "present": false
        },
        {
          "value": 120.0,
          "factor": "systolic_bp_lt_90",
          "points": 0,
          "present": 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": "Quinn JV, Stiell IG, McDermott DA, Sellers KL, Kohn MA, Wells GA",
        "doi": "10.1016/S0196-0644(03)00823-0",
        "id": "quinn-2004",
        "source": "Ann Emerg Med. 2004;43(2):224-232",
        "title": "Derivation of the San Francisco Syncope Rule to predict patients with short-term serious outcomes"
      },
      "formula": "sf_syncope",
      "formula_expression": "CHESS = chf + hematocrit_lt_30 + abnormal_ecg + shortness_of_breath + systolic_bp_lt_90; rule-positive if score ≥ 1; max 5",
      "max_score": 5,
      "score": 0,
      "hematocrit_percent": 40.0,
      "systolic_bp_mm_hg": 120.0,
      "rule_positive": false
    },
    {
      "components": [
        {
          "factor": "chf",
          "points": 0,
          "present": false
        },
        {
          "value": 40.0,
          "factor": "hematocrit_lt_30",
          "points": 0,
          "present": false
        },
        {
          "factor": "abnormal_ecg",
          "points": 0,
          "present": false
        },
        {
          "factor": "shortness_of_breath",
          "points": 0,
          "present": false
        },
        {
          "value": 120.0,
          "factor": "systolic_bp_lt_90",
          "points": 0,
          "present": 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": "Quinn JV, Stiell IG, McDermott DA, Sellers KL, Kohn MA, Wells GA",
        "doi": "10.1016/S0196-0644(03)00823-0",
        "id": "quinn-2004",
        "source": "Ann Emerg Med. 2004;43(2):224-232",
        "title": "Derivation of the San Francisco Syncope Rule to predict patients with short-term serious outcomes"
      },
      "formula": "sf_syncope",
      "formula_expression": "CHESS = chf + hematocrit_lt_30 + abnormal_ecg + shortness_of_breath + systolic_bp_lt_90; rule-positive if score ≥ 1; max 5",
      "max_score": 5,
      "score": 0,
      "hematocrit_percent": 40.0,
      "systolic_bp_mm_hg": 120.0,
      "rule_positive": false
    }
  ]
}

Response

Field	Type	Description
`formula`	string	sf_syncope
`formula_expression`	string	Exact expression used
`score`	integer	Count of positive CHESS criteria (0-5)
`max_score`	integer	Always 5
`rule_positive`	boolean	true when score ≥ 1 (any CHESS criterion). Not a diagnosis.
`hematocrit_percent`	number	Hematocrit used for the <30 cutoff
`systolic_bp_mm_hg`	number	Systolic BP used for the <90 cutoff
`components`	array	Per-factor points
`citation`	object	Ann Emerg Med 2004 citation
`disclaimer`	string	Not-a-device notice

Example JSON

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

{
  "components": [
    {
      "factor": "chf",
      "points": 0,
      "present": false
    },
    {
      "value": 40.0,
      "factor": "hematocrit_lt_30",
      "points": 0,
      "present": false
    },
    {
      "factor": "abnormal_ecg",
      "points": 0,
      "present": false
    },
    {
      "factor": "shortness_of_breath",
      "points": 0,
      "present": false
    },
    {
      "value": 120.0,
      "factor": "systolic_bp_lt_90",
      "points": 0,
      "present": 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": "Quinn JV, Stiell IG, McDermott DA, Sellers KL, Kohn MA, Wells GA",
    "doi": "10.1016/S0196-0644(03)00823-0",
    "id": "quinn-2004",
    "source": "Ann Emerg Med. 2004;43(2):224-232",
    "title": "Derivation of the San Francisco Syncope Rule to predict patients with short-term serious outcomes"
  },
  "formula": "sf_syncope",
  "formula_expression": "CHESS = chf + hematocrit_lt_30 + abnormal_ecg + shortness_of_breath + systolic_bp_lt_90; rule-positive if score ≥ 1; max 5",
  "max_score": 5,
  "score": 0,
  "hematocrit_percent": 40.0,
  "systolic_bp_mm_hg": 120.0,
  "rule_positive": false
}

Client errors (HTTP 400)

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

HTTP	Code	When
400	`invalid_flag`	boolean clinical flags must be true or false Returned before settlement; you are not charged.
400	`invalid_hematocrit`	hematocrit_percent must be a number from 10 to 70. Returned before settlement; you are not charged.
400	`invalid_systolic_bp`	systolic_mm_hg or systolic_bp_mm_hg must be a number from 50 to 250. Returned before settlement; you are not charged.
400	`invalid_items`	POST body must be a JSON object with only an items array Returned before settlement; you are not charged.
400	`invalid_item_count`	items must be an array of 1 to 25 objects Returned before settlement; you are not charged.
400	`invalid_item`	each items entry must be a JSON object Returned before settlement; you are not charged.

Related tools

Glasgow Coma Scale — Compute the Glasgow Coma Scale as the sum of caller-assigned eye, verbal, and motor integers. The 1974 or 1976 edition is required.

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.