# Palchak pediatric head trauma

Palchak pediatric head trauma

Status: LIVE
Price: $0.005 USDC
`GET /api/calc/palchak`
HTML: https://magentlab.com/docs/palchak
Markdown: https://magentlab.com/docs/palchak.md

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

## What it computes

Apply the Palchak 2003 derivation and return high or low risk of brain injury from five caller-assigned findings after blunt head trauma in a child 0-17 years. Scalp hematoma scores only when age is 0, 1, or 2.

## When to use

When an agent has caller-assigned findings after blunt head trauma in a child 0-17 years and needs the Palchak 2003 low-risk rule, not PECARN, CATCH, CHALICE, Canadian CT Head, or NEXUS.

## When not to use

- Not a medical device. Not a diagnosis. magent does not examine the child or order CT.
- This tool is the Palchak 2003 derivation only. It is not PECARN, not CATCH, not CHALICE, not the Canadian CT Head Rule, and not NEXUS.
- Age is integer years 0-17. Scalp hematoma counts toward high risk only when age is 0, 1, or 2; the flag is parsed but does not score at age 3-17.
- Headache is a published Palchak 2003 predictor and is scored at all ages 0-17 as assigned by the caller.
- The caller assigns all five findings. magent does not examine the child.

## Formula

```
high if any applicable predictor (abnormal_mental_status, clinical_signs_skull_fracture, history_of_vomiting, scalp_hematoma only if age <= 2, headache); else low; ct_not_low_risk iff high
```

## Citation

[A decision rule for identifying children at low risk for brain injuries after blunt head trauma](https://doi.org/10.1067/S0196-0644(03)00425-6)
Palchak MJ, Holmes JF, Vance CW, et al.
Ann Emerg Med. 2003;42(4):492-506
DOI: [10.1067/S0196-0644(03)00425-6](https://doi.org/10.1067/S0196-0644(03)00425-6)

## Worked example

### Age 10, all five flags false

Given: `abnormal_mental_status=false, age=10, clinical_signs_skull_fracture=false, headache=false, history_of_vomiting=false, scalp_hematoma=false`

1. Age 10 is in range (0-17); scalp hematoma would not score at this age
2. No applicable predictor (abnormal mental status, clinical signs of skull fracture, history of vomiting, or headache)
3. low_risk is true; high_risk and ct_not_low_risk are false


### Age 2 scalp hematoma is high risk

Given: `abnormal_mental_status=false, age=2, clinical_signs_skull_fracture=false, headache=false, history_of_vomiting=false, scalp_hematoma=true`

1. Age 2 is <= 2, so scalp hematoma is an applicable predictor
2. high_risk and ct_not_low_risk are true; magent does not order CT


### Age 3 scalp hematoma stays low risk

Given: `abnormal_mental_status=false, age=3, clinical_signs_skull_fracture=false, headache=false, history_of_vomiting=false, scalp_hematoma=true`

1. Age 3 is >= 3, so scalp hematoma is parsed but does not score
2. No other predictor is present; low_risk is true


## Also searched as

- Palchak rule
- Palchak 2003
- Palchak head trauma
- Palchak pediatric head CT
- Palchak decision rule
- Palchak blunt head trauma
- children low risk brain injury Palchak
- Palchak 2003 Ann Emerg Med

## Parameters

- `age` (integer, required): Age in years (integer 0-17). Scalp hematoma is a high-risk predictor only when age is 0, 1, or 2; age 3-17 parse scalp_hematoma but do not score it. Age 18 is rejected.
- `abnormal_mental_status` (boolean, required): Abnormal mental status as assigned by the caller. true or false. High-risk at all ages 0-17. magent does not examine the child or assign GCS.
- `clinical_signs_skull_fracture` (boolean, required): Clinical signs of skull fracture as assigned by the caller. true or false. High-risk at all ages 0-17. magent does not examine the child or read a radiograph.
- `history_of_vomiting` (boolean, required): History of vomiting as assigned by the caller. true or false. High-risk at all ages 0-17.
- `scalp_hematoma` (boolean, required): Scalp hematoma as assigned by the caller. true or false. High-risk only when age is 0, 1, or 2; parsed but not scored when age >= 3. magent does not examine the scalp.
- `headache` (boolean, required): Headache as assigned by the caller. true or false. High-risk at all ages 0-17 (Palchak 2003 listed headache as a predictor). magent does not examine the child.

## 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.

Method: `POST /api/calc/palchak`
Max items: 25
Price: unit_amount + extra_item_amount * (n - 1) (unit 5000 atomic, extra 2000 atomic)
Status: 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:

```json
{
  "items": [
    {
      "abnormal_mental_status": "false",
      "age": "10",
      "clinical_signs_skull_fracture": "false",
      "headache": "false",
      "history_of_vomiting": "false",
      "scalp_hematoma": "false"
    },
    {
      "abnormal_mental_status": "false",
      "age": "10",
      "clinical_signs_skull_fracture": "false",
      "headache": "false",
      "history_of_vomiting": "false",
      "scalp_hematoma": "false"
    }
  ]
}
```

Human paywall (two-item fixture): https://api.magentlab.com/paywall/bulk/palchak

Example 200:

```json
{
  "count": 2,
  "path": "/api/calc/palchak",
  "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": "Palchak MJ, Holmes JF, Vance CW, et al.",
        "doi": "10.1067/S0196-0644(03)00425-6",
        "id": "palchak-2003",
        "pmid": "14520320",
        "source": "Ann Emerg Med. 2003;42(4):492-506",
        "title": "A decision rule for identifying children at low risk for brain injuries after blunt head trauma"
      },
      "formula": "palchak",
      "formula_expression": "high if any applicable predictor (abnormal_mental_status, clinical_signs_skull_fracture, history_of_vomiting, scalp_hematoma only if age <= 2, headache); else low; ct_not_low_risk iff high",
      "age_years": 10,
      "low_risk": true,
      "criteria": [
        {
          "factor": "abnormal_mental_status",
          "met": false
        },
        {
          "factor": "clinical_signs_skull_fracture",
          "met": false
        },
        {
          "factor": "history_of_vomiting",
          "met": false
        },
        {
          "factor": "scalp_hematoma",
          "met": false
        },
        {
          "factor": "headache",
          "met": false
        }
      ],
      "high_risk": false,
      "ct_not_low_risk": 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": "Palchak MJ, Holmes JF, Vance CW, et al.",
        "doi": "10.1067/S0196-0644(03)00425-6",
        "id": "palchak-2003",
        "pmid": "14520320",
        "source": "Ann Emerg Med. 2003;42(4):492-506",
        "title": "A decision rule for identifying children at low risk for brain injuries after blunt head trauma"
      },
      "formula": "palchak",
      "formula_expression": "high if any applicable predictor (abnormal_mental_status, clinical_signs_skull_fracture, history_of_vomiting, scalp_hematoma only if age <= 2, headache); else low; ct_not_low_risk iff high",
      "age_years": 10,
      "low_risk": true,
      "criteria": [
        {
          "factor": "abnormal_mental_status",
          "met": false
        },
        {
          "factor": "clinical_signs_skull_fracture",
          "met": false
        },
        {
          "factor": "history_of_vomiting",
          "met": false
        },
        {
          "factor": "scalp_hematoma",
          "met": false
        },
        {
          "factor": "headache",
          "met": false
        }
      ],
      "high_risk": false,
      "ct_not_low_risk": false
    }
  ]
}
```

## Response fields

- `formula` (string): palchak
- `formula_expression` (string): Palchak 2003 any-applicable-predictor high then low rule
- `age_years` (integer): Age in years used for the scalp-hematoma age gate (scores only if age <= 2)
- `high_risk` (boolean): true when any age-applicable Palchak 2003 predictor is present. Mutually exclusive with low_risk. Not a diagnosis and not a CT order.
- `low_risk` (boolean): true when no age-applicable Palchak 2003 predictor is present (the negation of high_risk)
- `ct_not_low_risk` (boolean): true when high_risk is true. Not a CT order. magent does not order CT.
- `criteria` (array): Per-factor rows with factor and met. scalp_hematoma is met only when the flag is true and age is 0, 1, or 2.
- `citation` (object): Palchak 2003 Ann Emerg Med 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": "Palchak MJ, Holmes JF, Vance CW, et al.",
    "doi": "10.1067/S0196-0644(03)00425-6",
    "id": "palchak-2003",
    "pmid": "14520320",
    "source": "Ann Emerg Med. 2003;42(4):492-506",
    "title": "A decision rule for identifying children at low risk for brain injuries after blunt head trauma"
  },
  "formula": "palchak",
  "formula_expression": "high if any applicable predictor (abnormal_mental_status, clinical_signs_skull_fracture, history_of_vomiting, scalp_hematoma only if age <= 2, headache); else low; ct_not_low_risk iff high",
  "age_years": 10,
  "low_risk": true,
  "criteria": [
    {
      "factor": "abnormal_mental_status",
      "met": false
    },
    {
      "factor": "clinical_signs_skull_fracture",
      "met": false
    },
    {
      "factor": "history_of_vomiting",
      "met": false
    },
    {
      "factor": "scalp_hematoma",
      "met": false
    },
    {
      "factor": "headache",
      "met": false
    }
  ],
  "high_risk": false,
  "ct_not_low_risk": false
}
```

## Errors

- HTTP 400 `invalid_palchak_age`: age must be an integer from 0 to 17 (Palchak 2003 pediatric blunt head trauma). 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

- [PECARN pediatric head CT](https://magentlab.com/docs/pecarn-head) — Apply the Kuppermann 2009 PECARN prediction trees and return high, intermediate, or low risk of clinically important brain injury from caller-assigned findings after pediatric head trauma.
- [CATCH](https://magentlab.com/docs/catch) — Apply the Osmond 2010 CATCH derivation and return high, medium, or low risk plus whether CT of the head is indicated from seven caller-assigned findings after pediatric minor head injury.
- [CHALICE](https://magentlab.com/docs/chalice) — Apply the Dunning 2006 CHALICE rule and return whether CT is required from caller-assigned history, examination, and mechanism findings after head injury in a child younger than 16.
- [Canadian CT Head Rule](https://magentlab.com/docs/canadian-ct-head) — Apply the Stiell 2001 Canadian CT Head Rule and return whether CT is indicated from caller-assigned high-risk and medium-risk findings after minor blunt head injury.

## 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.

- 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 accepts[0] (exact, EIP-3009) with validBefore = now + maxTimeoutSeconds (600 seconds), or accepts[1] (batch-settlement deposit/voucher) on product GET. Ping and POST {items} stay exact. Magent retries transient facilitator 429/5xx before answering.
- Retry the same URL with PAYMENT-SIGNATURE (base64 JSON of accepted and payload). Magent attaches canonical extensions.bazaar on CDP verify/settle; echoing 402 bazaar is optional.
- Success is HTTP 200 JSON plus PAYMENT-RESPONSE. exact settles before the tool. batch-settlement verifies (and deposit-settles) before the tool and commits the charge after HTTP 2xx. HTTP 503: retry the same PAYMENT-SIGNATURE. Mint a new exact 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.
- offered `batch-settlement` on eip155:8453: Payment-channel vouchers claimed later in batches. Exact stays accepts[0]. Same-path POST {items} is still exact. extra.assetTransferMethod=eip3009 extra.paymentFlow=authorization.

- 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.

Same-path POST {items} is still scheme exact: one EIP-3009 authorization for GET unit plus $0.002 per extra item. 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

- 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.