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Canadian CT Head Rule Calculator (Stiell 2001)
x402
Canadian CT Head Rule Calculator (Stiell 2001) is a paid API for AI agents from api.magentlab.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-10).
Applies the validated Canadian CT Head Rule to determine whether CT imaging is indicated for a minor head injury patient based on high-risk and medium-risk clinical factors.
Price / call$0.005
Success—
StatusUnknown
How this service works
Deterministic published-formula arithmetic plus ICD-10-CM, RxNorm, and LOINC. Pay in USDC on Base via x402.
Output
Returns whether CT is indicated (true/false) based on the Canadian CT Head Rule, along with which high-risk or medium-risk factors were positive and the clinical basis for the recommendation.
Example use cases
ED triage CT head decision
“I have a 68-year-old who fell down 6 stairs and hit their head. GCS is 15 at 2 hours, no open or depressed skull fracture suspected, no basal skull fracture signs, vomited twice, no amnesia before impact, and the mechanism was a fall from more than 3 feet. Run the Canadian CT Head Rule and tell me if CT is indicated.”
Dangerous mechanism assessment in younger patient
“My 34-year-old patient was a pedestrian struck by a car and has a minor head injury. GCS is 15 at 2 hours, no skull fracture signs, no vomiting, but there's amnesia before impact of about 45 minutes. Apply the Canadian CT Head Rule — does this patient need a CT?”
Ruling out CT for low-risk head injury
“Patient is 45 years old with a minor head injury from a simple ground-level fall. GCS is 15 at 2 hours after injury, no suspected open or depressed skull fracture, no basal skull fracture signs, no vomiting, no amnesia before impact, and the mechanism wasn't dangerous. Per the Canadian CT Head Rule, is CT indicated?”
Technical details
Endpoint
GEThttps://api.magentlab.com/api/calc/canadian_ct_head?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need a deterministic, published clinical decision rule for CT head ordering in adult patients (≥16 years) with minor head injury. Prefer this over NEXUS (cervical spine), PECARN (pediatric head), or CATCH (Canadian pediatric) for adult head CT decisions. Ideal for embedding evidence-based clinical decision support in triage workflows, EHR integrations, or telehealth platforms where the caller has already assessed and can provide the required clinical flags.
Side effects
- Age outside valid range (must be 16-120) returns an error
- Missing required boolean parameters returns a validation error
- Rule is not applicable for patients under 16 (pediatric — use PECARN or CATCH instead)
- Caller must pre-classify all boolean flags; the API does not interpret free-text clinical notes
- Does not replace physician judgment or account for factors outside the published rule
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"path": "/api/calc/canadian_ct_head",
"count": 2,
"items": [
{
"formula": "canadian_ct_head",
"citation": {
"id": "stiell-2001-ct-head",
"doi": "10.1016/S0140-6736(00)04561-X",
"title": "The Canadian CT Head Rule for patients with minor head injury",
"source": "Lancet. 2001;357(9266):1391-1396",
"authors": "Stiell IG, Wells GA, Vandemheen K, et al."
},
"criteria": [
{
"met": false,
"factor": "gcs_lt_15_at_2h"
},
{
"met": false,
"factor": "suspected_open_or_depressed_skull_fx"
},
{
"met": false,
"factor": "any_sign_basal_skull_fx"
},
{
"met": false,
"factor": "vomiting_two_or_more"
},
{
"met": false,
"value": 40,
"factor": "age_ge_65"
},
{
"met": false,
"factor": "amnesia_before_impact_gt_30min"
},
{
"met": false,
"factor": "dangerous_mechanism"
}
],
"age_years": 40,
"high_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.",
"medium_risk": false,
"ct_indicated": false,
"formula_expression": "ct indicated if any high-risk (gcs_lt_15_at_2h or suspected_open_or_depressed_skull_fx or any_sign_basal_skull_fx or vomiting_two_or_more or age >= 65) or any medium-risk (amnesia_before_impact_gt_30min or dangerous_mechanism)"
},
{
"formula": "canadian_ct_head",
"citation": {
"id": "stiell-2001-ct-head",
"doi": "10.1016/S0140-6736(00)04561-X",
"title": "The Canadian CT Head Rule for patients with minor head injury",
"source": "Lancet. 2001;357(9266):1391-1396",
"authors": "Stiell IG, Wells GA, Vandemheen K, et al."
},
"criteria": [
{
"met": false,
"factor": "gcs_lt_15_at_2h"
},
{
"met": false,
"factor": "suspected_open_or_depressed_skull_fx"
},
{
"met": false,
"factor": "any_sign_basal_skull_fx"
},
{
"met": false,
"factor": "vomiting_two_or_more"
},
{
"met": false,
"value": 40,
"factor": "age_ge_65"
},
{
"met": false,
"factor": "amnesia_before_impact_gt_30min"
},
{
"met": false,
"factor": "dangerous_mechanism"
}
],
"age_years": 40,
"high_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.",
"medium_risk": false,
"ct_indicated": false,
"formula_expression": "ct indicated if any high-risk (gcs_lt_15_at_2h or suspected_open_or_depressed_skull_fx or any_sign_basal_skull_fx or vomiting_two_or_more or age >= 65) or any medium-risk (amnesia_before_impact_gt_30min or dangerous_mechanism)"
}
]
}
}Tags
x402
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