MAGENT

Emergency · LIVE

CHIP prediction rule

CHIP

Apply the Smits 2007 simple CHIP rule and return whether CT is indicated from caller-assigned major and minor findings plus GCS and age after minor head injury.

LIVE $0.005 USDC GET /api/calc/chip

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

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

What it computes

Apply the Smits 2007 simple CHIP rule and return whether CT is indicated from caller-assigned major and minor findings plus GCS and age after minor head injury.

When to use

When an agent has caller-assigned findings after blunt head trauma in a patient 16 or older with GCS 13-15 as published and needs the 2007 simple CHIP rule, not Canadian CT Head, NEXUS Head CT, PECARN, New Orleans, or the 2022 CHIP update.

When not to use

  • Not a medical device. Not a diagnosis of intracranial injury. magent does not examine the patient.
  • magent does not interpret imaging or order a CT. This tool returns whether CT is indicated by the published simple CHIP rule only.
  • Smits 2007 simple rule only (CT if ≥1 major or ≥2 minor). Not the detailed CHIP logistic model and not the 2022 CHIP update (different coefficients; drops anticoagulants; adds antiplatelet).
  • Not the Canadian CT Head Rule, not NEXUS Head CT, not New Orleans, and not PECARN. Published for adults ≥16 years with GCS 13-15.
  • The caller assigns every clinical flag. GCS is an integer 13-15. Age is an integer ≥16. magent does not assign GCS, classify mechanism, or read a coagulation assay.
  • PTA ≥4 h is major; PTA of 2 to <4 h is minor. GCS deterioration ≥2 points at 1 hour is major; 1 point is minor. Age ≥60 is major; age 40-59 is the 40-60 y minor band.

Formula

ct indicated if ≥1 major (pedestrian_or_cyclist_vs_vehicle, ejected_from_vehicle, vomiting, pta_ge_4h, clinical_signs_skull_fracture, gcs < 15, gcs_deterioration_ge_2, anticoagulant_therapy, posttraumatic_seizure, age ≥ 60) or ≥2 minor (fall_from_any_elevation, persistent_anterograde_amnesia, pta_2_to_lt_4h, skull_contusion, neurologic_deficit, loss_of_consciousness, gcs_deterioration_1, age 40-60)

Citation

Title
Predicting intracranial traumatic findings on computed tomography in patients with minor head injury: the CHIP prediction rule
Authors
Smits M, Dippel DW, Steyerberg EW, et al.
Source
Ann Intern Med. 2007;146(6):397-405
DOI
10.7326/0003-4819-146-6-200703200-00004

Worked example

GCS 15 and all flags false

Given: age=30anticoagulant_therapy=falseclinical_signs_skull_fracture=falseejected_from_vehicle=falsefall_from_any_elevation=falsegcs=15gcs_deterioration_1=falsegcs_deterioration_ge_2=falseloss_of_consciousness=falseneurologic_deficit=falsepedestrian_or_cyclist_vs_vehicle=falsepersistent_anterograde_amnesia=falseposttraumatic_seizure=falsepta_2_to_lt_4h=falsepta_ge_4h=falseskull_contusion=falsevomiting=false

  1. GCS 15 is not a major criterion; age 30 is neither ≥60 nor the 40-60 y minor band
  2. All major and minor flags are false (0 major, 0 minor)
  3. CT is not indicated by the simple rule

One major (vomiting)

Given: age=30anticoagulant_therapy=falseclinical_signs_skull_fracture=falseejected_from_vehicle=falsefall_from_any_elevation=falsegcs=15gcs_deterioration_1=falsegcs_deterioration_ge_2=falseloss_of_consciousness=falseneurologic_deficit=falsepedestrian_or_cyclist_vs_vehicle=falsepersistent_anterograde_amnesia=falseposttraumatic_seizure=falsepta_2_to_lt_4h=falsepta_ge_4h=falseskull_contusion=falsevomiting=true

  1. Vomiting is a major criterion
  2. CT is indicated (≥1 major)

Two minors without a major

Given: age=30anticoagulant_therapy=falseclinical_signs_skull_fracture=falseejected_from_vehicle=falsefall_from_any_elevation=truegcs=15gcs_deterioration_1=falsegcs_deterioration_ge_2=falseloss_of_consciousness=trueneurologic_deficit=falsepedestrian_or_cyclist_vs_vehicle=falsepersistent_anterograde_amnesia=falseposttraumatic_seizure=falsepta_2_to_lt_4h=falsepta_ge_4h=falseskull_contusion=falsevomiting=false

  1. No major criterion
  2. Fall from any elevation and loss of consciousness are two minor criteria
  3. CT is indicated (≥2 minor)

Also searched as

  • CHIP
  • CHIP prediction rule
  • CT in Head Injury Patients
  • Smits 2007 CHIP
  • CHIP head CT rule
  • simple CHIP rule
  • CHIP major minor criteria
  • Smits CHIP

Try

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

/api/calc/chip?age=30&gcs=15&pedestrian_or_cyclist_vs_vehicle=false&ejected_from_vehicle=false&vomiting=false&pta_ge_4h=false&clinical_signs_skull_fracture=false&gcs_deterioration_ge_2=false&anticoagulant_therapy=false&posttraumatic_seizure=false&fall_from_any_elevation=false&persistent_anterograde_amnesia=false&pta_2_to_lt_4h=false&skull_contusion=false&neurologic_deficit=false&loss_of_consciousness=false&gcs_deterioration_1=false

Full URL: https://api.magentlab.com/api/calc/chip?age=30&gcs=15&pedestrian_or_cyclist_vs_vehicle=false&ejected_from_vehicle=false&vomiting=false&pta_ge_4h=false&clinical_signs_skull_fracture=false&gcs_deterioration_ge_2=false&anticoagulant_therapy=false&posttraumatic_seizure=false&fall_from_any_elevation=false&persistent_anterograde_amnesia=false&pta_2_to_lt_4h=false&skull_contusion=false&neurologic_deficit=false&loss_of_consciousness=false&gcs_deterioration_1=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/chip?age=30&gcs=15&pedestrian_or_cyclist_vs_vehicle=false&ejected_from_vehicle=false&vomiting=false&pta_ge_4h=false&clinical_signs_skull_fracture=false&gcs_deterioration_ge_2=false&anticoagulant_therapy=false&posttraumatic_seizure=false&fall_from_any_elevation=false&persistent_anterograde_amnesia=false&pta_2_to_lt_4h=false&skull_contusion=false&neurologic_deficit=false&loss_of_consciousness=false&gcs_deterioration_1=false"

Parameters

Name Type Required Description
age integer required Age in years (integer 16-120). Age ≥60 is a major criterion. Age 40-59 is the 40-60 y minor band; 39 is neither. The published rule is for patients ≥16 years.
gcs integer required Glasgow Coma Scale integer 13-15 as published. GCS 13 or 14 (GCS <15) is a major criterion; 15 is not. magent does not assign GCS from an exam.
pedestrian_or_cyclist_vs_vehicle boolean required Pedestrian or cyclist versus vehicle (Smits 2007 major). true or false as assigned by the caller. magent does not classify mechanism.
ejected_from_vehicle boolean required Ejected from vehicle (Smits 2007 major). true or false as assigned by the caller. magent does not classify mechanism.
vomiting boolean required Vomiting (Smits 2007 major). true or false as assigned by the caller. magent does not take a vomit count.
pta_ge_4h boolean required Posttraumatic amnesia ≥4 hours (Smits 2007 major). true or false as assigned by the caller. Mutually exclusive with pta_2_to_lt_4h. magent does not measure amnesia duration.
clinical_signs_skull_fracture boolean required Clinical signs of skull fracture (Smits 2007 major): any injury that suggests a skull fracture, such as palpable discontinuity of the skull, leakage of cerebrospinal fluid, raccoon-eye bruising, and bleeding from the ear, as assigned by the caller. true or false. magent does not examine the patient.
gcs_deterioration_ge_2 boolean required GCS deterioration ≥2 points 1 hour after presentation (Smits 2007 major). true or false as assigned by the caller. Mutually exclusive with gcs_deterioration_1. magent does not assign GCS change.
anticoagulant_therapy boolean required Use of anticoagulant therapy (Smits 2007 major). true or false as assigned by the caller. This is the 2007 simple rule, not the 2022 CHIP update. magent does not interpret a coagulation assay.
posttraumatic_seizure boolean required Posttraumatic seizure (Smits 2007 major). true or false as assigned by the caller. magent does not witness a seizure.
fall_from_any_elevation boolean required Fall from any elevation (Smits 2007 minor). true or false as assigned by the caller. magent does not classify mechanism.
persistent_anterograde_amnesia boolean required Persistent anterograde amnesia, any deficit of short-term memory (Smits 2007 minor). true or false as assigned by the caller. magent does not test memory.
pta_2_to_lt_4h boolean required Posttraumatic amnesia of 2 to <4 hours (Smits 2007 minor). true or false as assigned by the caller. Mutually exclusive with pta_ge_4h. magent does not measure amnesia duration.
skull_contusion boolean required Contusion of the skull (Smits 2007 minor). true or false as assigned by the caller. magent does not examine the scalp.
neurologic_deficit boolean required Neurologic deficit (Smits 2007 minor). true or false as assigned by the caller. magent does not examine the patient.
loss_of_consciousness boolean required Loss of consciousness (Smits 2007 minor). true or false as assigned by the caller. magent does not take a history.
gcs_deterioration_1 boolean required GCS deterioration of 1 point 1 hour after presentation (Smits 2007 minor). true or false as assigned by the caller. Mutually exclusive with gcs_deterioration_ge_2. magent does not assign GCS change.

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/chip 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": [
    {
      "age": "30",
      "anticoagulant_therapy": "false",
      "clinical_signs_skull_fracture": "false",
      "ejected_from_vehicle": "false",
      "fall_from_any_elevation": "false",
      "gcs": "15",
      "gcs_deterioration_1": "false",
      "gcs_deterioration_ge_2": "false",
      "loss_of_consciousness": "false",
      "neurologic_deficit": "false",
      "pedestrian_or_cyclist_vs_vehicle": "false",
      "persistent_anterograde_amnesia": "false",
      "posttraumatic_seizure": "false",
      "pta_2_to_lt_4h": "false",
      "pta_ge_4h": "false",
      "skull_contusion": "false",
      "vomiting": "false"
    },
    {
      "age": "30",
      "anticoagulant_therapy": "false",
      "clinical_signs_skull_fracture": "false",
      "ejected_from_vehicle": "false",
      "fall_from_any_elevation": "false",
      "gcs": "15",
      "gcs_deterioration_1": "false",
      "gcs_deterioration_ge_2": "false",
      "loss_of_consciousness": "false",
      "neurologic_deficit": "false",
      "pedestrian_or_cyclist_vs_vehicle": "false",
      "persistent_anterograde_amnesia": "false",
      "posttraumatic_seizure": "false",
      "pta_2_to_lt_4h": "false",
      "pta_ge_4h": "false",
      "skull_contusion": "false",
      "vomiting": "false"
    }
  ]
}

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/chip",
  "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": "Smits M, Dippel DW, Steyerberg EW, et al.",
        "doi": "10.7326/0003-4819-146-6-200703200-00004",
        "id": "smits-2007",
        "pmid": "17371884",
        "source": "Ann Intern Med. 2007;146(6):397-405",
        "title": "Predicting intracranial traumatic findings on computed tomography in patients with minor head injury: the CHIP prediction rule"
      },
      "formula": "chip",
      "formula_expression": "ct indicated if ≥1 major (pedestrian_or_cyclist_vs_vehicle, ejected_from_vehicle, vomiting, pta_ge_4h, clinical_signs_skull_fracture, gcs < 15, gcs_deterioration_ge_2, anticoagulant_therapy, posttraumatic_seizure, age ≥ 60) or ≥2 minor (fall_from_any_elevation, persistent_anterograde_amnesia, pta_2_to_lt_4h, skull_contusion, neurologic_deficit, loss_of_consciousness, gcs_deterioration_1, age 40-60)",
      "age_years": 30,
      "criteria": [
        {
          "factor": "pedestrian_or_cyclist_vs_vehicle",
          "met": false
        },
        {
          "factor": "ejected_from_vehicle",
          "met": false
        },
        {
          "factor": "vomiting",
          "met": false
        },
        {
          "factor": "pta_ge_4h",
          "met": false
        },
        {
          "factor": "clinical_signs_skull_fracture",
          "met": false
        },
        {
          "value": 15,
          "factor": "gcs_lt_15",
          "met": false
        },
        {
          "factor": "gcs_deterioration_ge_2",
          "met": false
        },
        {
          "factor": "anticoagulant_therapy",
          "met": false
        },
        {
          "factor": "posttraumatic_seizure",
          "met": false
        },
        {
          "value": 30,
          "factor": "age_ge_60",
          "met": false
        },
        {
          "factor": "fall_from_any_elevation",
          "met": false
        },
        {
          "factor": "persistent_anterograde_amnesia",
          "met": false
        },
        {
          "factor": "pta_2_to_lt_4h",
          "met": false
        },
        {
          "factor": "skull_contusion",
          "met": false
        },
        {
          "factor": "neurologic_deficit",
          "met": false
        },
        {
          "factor": "loss_of_consciousness",
          "met": false
        },
        {
          "factor": "gcs_deterioration_1",
          "met": false
        },
        {
          "value": 30,
          "factor": "age_40_to_60",
          "met": false
        }
      ],
      "major_count": 0,
      "minor_count": 0,
      "ct_indicated": false,
      "gcs": 15
    },
    {
      "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": "Smits M, Dippel DW, Steyerberg EW, et al.",
        "doi": "10.7326/0003-4819-146-6-200703200-00004",
        "id": "smits-2007",
        "pmid": "17371884",
        "source": "Ann Intern Med. 2007;146(6):397-405",
        "title": "Predicting intracranial traumatic findings on computed tomography in patients with minor head injury: the CHIP prediction rule"
      },
      "formula": "chip",
      "formula_expression": "ct indicated if ≥1 major (pedestrian_or_cyclist_vs_vehicle, ejected_from_vehicle, vomiting, pta_ge_4h, clinical_signs_skull_fracture, gcs < 15, gcs_deterioration_ge_2, anticoagulant_therapy, posttraumatic_seizure, age ≥ 60) or ≥2 minor (fall_from_any_elevation, persistent_anterograde_amnesia, pta_2_to_lt_4h, skull_contusion, neurologic_deficit, loss_of_consciousness, gcs_deterioration_1, age 40-60)",
      "age_years": 30,
      "criteria": [
        {
          "factor": "pedestrian_or_cyclist_vs_vehicle",
          "met": false
        },
        {
          "factor": "ejected_from_vehicle",
          "met": false
        },
        {
          "factor": "vomiting",
          "met": false
        },
        {
          "factor": "pta_ge_4h",
          "met": false
        },
        {
          "factor": "clinical_signs_skull_fracture",
          "met": false
        },
        {
          "value": 15,
          "factor": "gcs_lt_15",
          "met": false
        },
        {
          "factor": "gcs_deterioration_ge_2",
          "met": false
        },
        {
          "factor": "anticoagulant_therapy",
          "met": false
        },
        {
          "factor": "posttraumatic_seizure",
          "met": false
        },
        {
          "value": 30,
          "factor": "age_ge_60",
          "met": false
        },
        {
          "factor": "fall_from_any_elevation",
          "met": false
        },
        {
          "factor": "persistent_anterograde_amnesia",
          "met": false
        },
        {
          "factor": "pta_2_to_lt_4h",
          "met": false
        },
        {
          "factor": "skull_contusion",
          "met": false
        },
        {
          "factor": "neurologic_deficit",
          "met": false
        },
        {
          "factor": "loss_of_consciousness",
          "met": false
        },
        {
          "factor": "gcs_deterioration_1",
          "met": false
        },
        {
          "value": 30,
          "factor": "age_40_to_60",
          "met": false
        }
      ],
      "major_count": 0,
      "minor_count": 0,
      "ct_indicated": false,
      "gcs": 15
    }
  ]
}

Response

Field Type Description
formula string chip
formula_expression string Smits 2007 simple CHIP rule: CT if ≥1 major or ≥2 minor
ct_indicated boolean true when ≥1 major criterion or ≥2 minor criteria are met (Smits 2007 simple rule). Not a diagnosis and not a CT order.
major_count integer Count of major criteria met (0-10)
minor_count integer Count of minor criteria met (0-8)
gcs integer GCS integer used for the GCS <15 major criterion
age_years integer Age used for the ≥60 major and 40-60 y minor bands
criteria array Per-factor rows with factor and met; gcs_lt_15 includes value (gcs); age_ge_60 and age_40_to_60 include value (age_years)
citation object Smits 2007 Ann Intern Med citation
disclaimer string Not-a-device notice

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": "Smits M, Dippel DW, Steyerberg EW, et al.",
    "doi": "10.7326/0003-4819-146-6-200703200-00004",
    "id": "smits-2007",
    "pmid": "17371884",
    "source": "Ann Intern Med. 2007;146(6):397-405",
    "title": "Predicting intracranial traumatic findings on computed tomography in patients with minor head injury: the CHIP prediction rule"
  },
  "formula": "chip",
  "formula_expression": "ct indicated if ≥1 major (pedestrian_or_cyclist_vs_vehicle, ejected_from_vehicle, vomiting, pta_ge_4h, clinical_signs_skull_fracture, gcs < 15, gcs_deterioration_ge_2, anticoagulant_therapy, posttraumatic_seizure, age ≥ 60) or ≥2 minor (fall_from_any_elevation, persistent_anterograde_amnesia, pta_2_to_lt_4h, skull_contusion, neurologic_deficit, loss_of_consciousness, gcs_deterioration_1, age 40-60)",
  "age_years": 30,
  "criteria": [
    {
      "factor": "pedestrian_or_cyclist_vs_vehicle",
      "met": false
    },
    {
      "factor": "ejected_from_vehicle",
      "met": false
    },
    {
      "factor": "vomiting",
      "met": false
    },
    {
      "factor": "pta_ge_4h",
      "met": false
    },
    {
      "factor": "clinical_signs_skull_fracture",
      "met": false
    },
    {
      "value": 15,
      "factor": "gcs_lt_15",
      "met": false
    },
    {
      "factor": "gcs_deterioration_ge_2",
      "met": false
    },
    {
      "factor": "anticoagulant_therapy",
      "met": false
    },
    {
      "factor": "posttraumatic_seizure",
      "met": false
    },
    {
      "value": 30,
      "factor": "age_ge_60",
      "met": false
    },
    {
      "factor": "fall_from_any_elevation",
      "met": false
    },
    {
      "factor": "persistent_anterograde_amnesia",
      "met": false
    },
    {
      "factor": "pta_2_to_lt_4h",
      "met": false
    },
    {
      "factor": "skull_contusion",
      "met": false
    },
    {
      "factor": "neurologic_deficit",
      "met": false
    },
    {
      "factor": "loss_of_consciousness",
      "met": false
    },
    {
      "factor": "gcs_deterioration_1",
      "met": false
    },
    {
      "value": 30,
      "factor": "age_40_to_60",
      "met": false
    }
  ],
  "major_count": 0,
  "minor_count": 0,
  "ct_indicated": false,
  "gcs": 15
}

Client errors (HTTP 400)

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

HTTP Code When
400 invalid_chip CHIP inputs must match Smits 2007 simple major/minor criteria from that paper only. 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

  • Canadian CT Head Rule — 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.
  • NEXUS Head CT — Apply the Mower 2017 NEXUS Head CT eight-criterion decision instrument and return whether the patient is low-risk (all eight caller-assigned criteria absent). CT may be omitted by this instrument when low-risk. Does not order a CT.
  • PECARN pediatric head CT — 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.

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.