# Pediatric NEXUS II Pediatric NEXUS II Status: LIVE Price: $0.005 USDC `GET /api/calc/pediatric_nexus_ii` HTML: https://magentlab.com/docs/pediatric-nexus-ii Markdown: https://magentlab.com/docs/pediatric-nexus-ii.md Not a medical device. Not a diagnosis, dose, or listing recommendation. ## What it computes Apply the Gupta 2018 Pediatric NEXUS II seven-criterion decision instrument and return whether the child is low-risk (all seven caller-assigned flags false). Age 0-17 is required but is not a score criterion. CT may be omitted by this instrument when low-risk. Does not order a CT. ## When to use When an agent has caller-assigned findings after blunt head trauma in a child (age 0-17) and needs the published Pediatric NEXUS II decision instrument, not Mower 2017 adult NEXUS Head CT, not PECARN, CATCH, or CHALICE, and not Hoffman 2000 NEXUS C-spine. ## When not to use - Not a medical device. Not a diagnosis. magent does not examine the patient. - Not a CT order. Low-risk means CT may be omitted by this instrument. Presence of a criterion does not mandate CT. Do not order a CT from this tool. - Not adult NEXUS Head CT. This tool is the Gupta 2018 seven-criterion Pediatric NEXUS II instrument, not the Mower 2017 adult eight-criterion NEXUS Head CT, not PECARN, CATCH, or CHALICE, and not Hoffman 2000 NEXUS C-spine. - Age 0-17 is required but is not a criterion: it matches the Gupta 2018 pediatric population and is not scored. Adult NEXUS Head CT age ≥ 65 is dropped. The seven clinical flags determine low_risk. ## Formula ``` low_risk iff no skull_fracture and no scalp_hematoma and no neurologic_deficit and no altered_alertness and no abnormal_behavior and no persistent_vomiting and no coagulopathy ``` ## Citation [Validation of the Pediatric NEXUS II Head Computed Tomography Decision Instrument for Selective Imaging of Pediatric Patients with Blunt Head Trauma.](https://doi.org/10.1111/acem.13431) Gupta M, Mower WR, Rodriguez RM, Hendey GW Acad Emerg Med. 2018;25(7):729-737 DOI: [10.1111/acem.13431](https://doi.org/10.1111/acem.13431) ## Worked example ### All seven flags false Given: `abnormal_behavior=false, age=10, altered_alertness=false, coagulopathy=false, neurologic_deficit=false, persistent_vomiting=false, scalp_hematoma=false, skull_fracture=false` 1. Age 10 is required (0-17) but is not a score criterion; no skull fracture, scalp hematoma, neurologic deficit, altered alertness, abnormal behavior, persistent vomiting, or coagulopathy 2. low_risk is true; CT may be omitted by this instrument. This tool does not order a CT ### Skull fracture is not low-risk Given: `abnormal_behavior=false, age=10, altered_alertness=false, coagulopathy=false, neurologic_deficit=false, persistent_vomiting=false, scalp_hematoma=false, skull_fracture=true` 1. Age 10 remains in range; skull_fracture is true and the other six flags remain false 2. low_risk is false. Presence of this criterion does not mandate CT ## Also searched as - Pediatric NEXUS II - Gupta Pediatric NEXUS II - Pediatric NEXUS II Head CT - NEXUS II pediatric head CT - Gupta 2018 Pediatric NEXUS II - pediatric blunt head trauma CT rule - seven-criterion Pediatric NEXUS II - Pediatric NEXUS II decision instrument ## Parameters - `age` (integer, required): Age in years (integer 0-17). Required to match the Gupta 2018 pediatric population but is not a score criterion. Age 18 is rejected. Adult NEXUS Head CT age ≥ 65 is dropped. - `skull_fracture` (boolean, required): Evidence of skull fracture as assigned by the caller. true means a skull-fracture finding is present and low_risk is false. true or false. magent does not examine the patient or read a radiograph. - `scalp_hematoma` (boolean, required): Scalp hematoma as assigned by the caller. true means a scalp hematoma is present and low_risk is false. true or false. magent does not examine the scalp. - `neurologic_deficit` (boolean, required): Neurologic deficit (neurosurgical deficits) as assigned by the caller. true means a deficit is present and low_risk is false. true or false. magent does not examine the patient. - `altered_alertness` (boolean, required): Altered level of alertness as assigned by the caller. true means alertness is altered and low_risk is false. true or false. magent does not assign GCS. - `abnormal_behavior` (boolean, required): Abnormal behavior as assigned by the caller. true means abnormal behavior is present and low_risk is false. true or false. magent does not examine the patient. - `persistent_vomiting` (boolean, required): Persistent vomiting as assigned by the caller. true means persistent vomiting is present and low_risk is false. true or false. magent does not take a vomit count. - `coagulopathy` (boolean, required): Coagulopathy as assigned by the caller. true means coagulopathy is present and low_risk is false. true or false. magent does not interpret a coagulation assay. ## 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/pediatric_nexus_ii` 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_behavior": "false", "age": "10", "altered_alertness": "false", "coagulopathy": "false", "neurologic_deficit": "false", "persistent_vomiting": "false", "scalp_hematoma": "false", "skull_fracture": "false" }, { "abnormal_behavior": "false", "age": "10", "altered_alertness": "false", "coagulopathy": "false", "neurologic_deficit": "false", "persistent_vomiting": "false", "scalp_hematoma": "false", "skull_fracture": "false" } ] } ``` Human paywall (two-item fixture): https://api.magentlab.com/paywall/bulk/pediatric-nexus-ii Example 200: ```json { "count": 2, "path": "/api/calc/pediatric_nexus_ii", "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": "Gupta M, Mower WR, Rodriguez RM, Hendey GW", "doi": "10.1111/acem.13431", "id": "gupta-2018", "pmid": "29665151", "source": "Acad Emerg Med. 2018;25(7):729-737", "title": "Validation of the Pediatric NEXUS II Head Computed Tomography Decision Instrument for Selective Imaging of Pediatric Patients with Blunt Head Trauma." }, "formula": "pediatric_nexus_ii", "formula_expression": "low_risk iff no skull_fracture and no scalp_hematoma and no neurologic_deficit and no altered_alertness and no abnormal_behavior and no persistent_vomiting and no coagulopathy", "age_years": 10, "criteria": [ { "factor": "no_skull_fracture", "met": true }, { "factor": "no_scalp_hematoma", "met": true }, { "factor": "no_neurologic_deficit", "met": true }, { "factor": "no_altered_alertness", "met": true }, { "factor": "no_abnormal_behavior", "met": true }, { "factor": "no_persistent_vomiting", "met": true }, { "factor": "no_coagulopathy", "met": true } ], "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": "Gupta M, Mower WR, Rodriguez RM, Hendey GW", "doi": "10.1111/acem.13431", "id": "gupta-2018", "pmid": "29665151", "source": "Acad Emerg Med. 2018;25(7):729-737", "title": "Validation of the Pediatric NEXUS II Head Computed Tomography Decision Instrument for Selective Imaging of Pediatric Patients with Blunt Head Trauma." }, "formula": "pediatric_nexus_ii", "formula_expression": "low_risk iff no skull_fracture and no scalp_hematoma and no neurologic_deficit and no altered_alertness and no abnormal_behavior and no persistent_vomiting and no coagulopathy", "age_years": 10, "criteria": [ { "factor": "no_skull_fracture", "met": true }, { "factor": "no_scalp_hematoma", "met": true }, { "factor": "no_neurologic_deficit", "met": true }, { "factor": "no_altered_alertness", "met": true }, { "factor": "no_abnormal_behavior", "met": true }, { "factor": "no_persistent_vomiting", "met": true }, { "factor": "no_coagulopathy", "met": true } ], "low_risk": true } ] } ``` ## Response fields - `formula` (string): pediatric_nexus_ii - `formula_expression` (string): Gupta 2018 seven-criterion Pediatric NEXUS II decision instrument - `low_risk` (boolean): true only when all seven flags are false. CT may be omitted by this instrument when true. Does not order a CT. Presence of a criterion does not mandate CT. Age is not a criterion. Not a diagnosis. - `age_years` (integer): Age in years used to match the Gupta 2018 pediatric population; not a score criterion - `criteria` (array): Per-factor rows with factor and met; met is true when that named finding is absent (no_skull_fracture, no_scalp_hematoma, no_neurologic_deficit, no_altered_alertness, no_abnormal_behavior, no_persistent_vomiting, no_coagulopathy) - `citation` (object): Gupta 2018 Acad 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": "Gupta M, Mower WR, Rodriguez RM, Hendey GW", "doi": "10.1111/acem.13431", "id": "gupta-2018", "pmid": "29665151", "source": "Acad Emerg Med. 2018;25(7):729-737", "title": "Validation of the Pediatric NEXUS II Head Computed Tomography Decision Instrument for Selective Imaging of Pediatric Patients with Blunt Head Trauma." }, "formula": "pediatric_nexus_ii", "formula_expression": "low_risk iff no skull_fracture and no scalp_hematoma and no neurologic_deficit and no altered_alertness and no abnormal_behavior and no persistent_vomiting and no coagulopathy", "age_years": 10, "criteria": [ { "factor": "no_skull_fracture", "met": true }, { "factor": "no_scalp_hematoma", "met": true }, { "factor": "no_neurologic_deficit", "met": true }, { "factor": "no_altered_alertness", "met": true }, { "factor": "no_abnormal_behavior", "met": true }, { "factor": "no_persistent_vomiting", "met": true }, { "factor": "no_coagulopathy", "met": true } ], "low_risk": true } ``` ## Errors - HTTP 400 `invalid_pediatric_nexus_age`: age must be an integer from 0 to 17 (Gupta 2018 Pediatric NEXUS II; age 18 is rejected). 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 - [NEXUS Head CT](https://magentlab.com/docs/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](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. ## 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.