PEN-FAST penicillin allergy rule

PEN-FAST

Sum the three Trubiano 2020 PEN-FAST flags for a reported penicillin allergy and return the 0–5 score, published risk group, and low_risk_for_testing (score < 3).

LIVE $0.005 USDC GET /api/calc/pen_fast

Markdown: /docs/pen-fast.md · Canonical: https://magentlab.com/docs/pen-fast

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

What it computes

Sum the three Trubiano 2020 PEN-FAST flags for a reported penicillin allergy and return the 0–5 score, published risk group, and low_risk_for_testing (score < 3).

When to use

When an agent has already assigned the three Trubiano 2020 PEN-FAST flags for a patient who reports penicillin allergy and needs the published point total and risk group. magent does not take an allergy history and does not diagnose allergy or issue a delabeling order.

When not to use

Not a medical device.
Not an allergy diagnosis and not a delabeling order.
magent does not take an allergy history.
Derived in adults ≥16 years reporting penicillin allergy (not other beta-lactams).
SCAR phenotypes were uncommon in derivation.
A score <3 was the paper's low-risk cutoff (NPV 96.3% in derivation) and does not replace specialist testing when indicated.

Formula

PEN-FAST = five_or_fewer_years_ago (true 2) + anaphylaxis_angioedema_or_scar (true 2) + treatment_required (true 1); Trubiano 2020; max 5; 0 very_low, 1-2 low, 3 moderate, 4-5 high; low_risk_for_testing iff score < 3

Citation

Title: Development and Validation of a Penicillin Allergy Clinical Decision Rule
Authors: Trubiano JA, Vogrin S, Chua KYL, et al.
Source: JAMA Intern Med. 2020;180(5):745-752
DOI: 10.1001/jamainternmed.2020.0403

Worked example

All three flags false

Given: anaphylaxis_angioedema_or_scar=falsefive_or_fewer_years_ago=falsetreatment_required=false

five_or_fewer_years_ago false → 0; anaphylaxis_angioedema_or_scar false → 0; treatment_required false → 0
Score = 0 (max 5); risk = very_low; low_risk_for_testing = true

All three flags true

Given: anaphylaxis_angioedema_or_scar=truefive_or_fewer_years_ago=truetreatment_required=true

five_or_fewer_years_ago true → 2; anaphylaxis_angioedema_or_scar true → 2; treatment_required true → 1
Score = 5 (max 5); risk = high; low_risk_for_testing = false

Also searched as

PEN FAST
penicillin allergy
PEN-FAST
Trubiano 2020
penicillin allergy clinical decision rule
penicillin allergy score
PENFAST

Try

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

/api/calc/pen_fast?five_or_fewer_years_ago=false&anaphylaxis_angioedema_or_scar=false&treatment_required=false

Full URL: https://api.magentlab.com/api/calc/pen_fast?five_or_fewer_years_ago=false&anaphylaxis_angioedema_or_scar=false&treatment_required=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/pen_fast?five_or_fewer_years_ago=false&anaphylaxis_angioedema_or_scar=false&treatment_required=false"

Parameters

Name	Type	Required	Description
`five_or_fewer_years_ago`	boolean	required	Allergy event 5 or fewer years ago as assigned by the caller (Trubiano 2020). true scores 2. magent does not take an allergy history.
`anaphylaxis_angioedema_or_scar`	boolean	required	Anaphylaxis/angioedema or potential SCAR as one 2-point criterion (Trubiano 2020). true scores 2; do not add both phenotypes separately. magent does not take an allergy history.
`treatment_required`	boolean	required	Treatment required for the allergy episode as assigned by the caller (Trubiano 2020). true scores 1. magent does not take an allergy history.

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/pen_fast 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": [
    {
      "anaphylaxis_angioedema_or_scar": "false",
      "five_or_fewer_years_ago": "false",
      "treatment_required": "false"
    },
    {
      "anaphylaxis_angioedema_or_scar": "false",
      "five_or_fewer_years_ago": "false",
      "treatment_required": "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/pen_fast",
  "items": [
    {
      "components": [
        {
          "factor": "five_or_fewer_years_ago",
          "points": 0,
          "present": false
        },
        {
          "factor": "anaphylaxis_angioedema_or_scar",
          "points": 0,
          "present": false
        },
        {
          "factor": "treatment_required",
          "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": "Trubiano JA, Vogrin S, Chua KYL, et al.",
        "doi": "10.1001/jamainternmed.2020.0403",
        "id": "trubiano-2020",
        "pmid": "32176248",
        "source": "JAMA Intern Med. 2020;180(5):745-752",
        "title": "Development and Validation of a Penicillin Allergy Clinical Decision Rule"
      },
      "formula": "pen_fast",
      "formula_expression": "PEN-FAST = five_or_fewer_years_ago (true 2) + anaphylaxis_angioedema_or_scar (true 2) + treatment_required (true 1); Trubiano 2020; max 5; 0 very_low, 1-2 low, 3 moderate, 4-5 high; low_risk_for_testing iff score < 3",
      "max_score": 5,
      "score": 0,
      "risk": "very_low",
      "low_risk_for_testing": true
    },
    {
      "components": [
        {
          "factor": "five_or_fewer_years_ago",
          "points": 0,
          "present": false
        },
        {
          "factor": "anaphylaxis_angioedema_or_scar",
          "points": 0,
          "present": false
        },
        {
          "factor": "treatment_required",
          "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": "Trubiano JA, Vogrin S, Chua KYL, et al.",
        "doi": "10.1001/jamainternmed.2020.0403",
        "id": "trubiano-2020",
        "pmid": "32176248",
        "source": "JAMA Intern Med. 2020;180(5):745-752",
        "title": "Development and Validation of a Penicillin Allergy Clinical Decision Rule"
      },
      "formula": "pen_fast",
      "formula_expression": "PEN-FAST = five_or_fewer_years_ago (true 2) + anaphylaxis_angioedema_or_scar (true 2) + treatment_required (true 1); Trubiano 2020; max 5; 0 very_low, 1-2 low, 3 moderate, 4-5 high; low_risk_for_testing iff score < 3",
      "max_score": 5,
      "score": 0,
      "risk": "very_low",
      "low_risk_for_testing": true
    }
  ]
}

Response

Field	Type	Description
`formula`	string	pen_fast
`formula_expression`	string	Exact expression used
`score`	integer	PEN-FAST points 0-5
`max_score`	integer	Always 5
`risk`	string	Trubiano 2020 risk group: very_low (0), low (1–2), moderate (3), or high (4–5). Not an allergy diagnosis.
`low_risk_for_testing`	boolean	true iff score < 3 (Trubiano 2020 low-risk cutoff). Not a delabeling order and not a substitute for specialist testing when indicated.
`components`	array	Per-flag points
`citation`	object	Trubiano 2020 JAMA Intern Med citation
`disclaimer`	string	Not-a-device notice

Example JSON

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

{
  "components": [
    {
      "factor": "five_or_fewer_years_ago",
      "points": 0,
      "present": false
    },
    {
      "factor": "anaphylaxis_angioedema_or_scar",
      "points": 0,
      "present": false
    },
    {
      "factor": "treatment_required",
      "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": "Trubiano JA, Vogrin S, Chua KYL, et al.",
    "doi": "10.1001/jamainternmed.2020.0403",
    "id": "trubiano-2020",
    "pmid": "32176248",
    "source": "JAMA Intern Med. 2020;180(5):745-752",
    "title": "Development and Validation of a Penicillin Allergy Clinical Decision Rule"
  },
  "formula": "pen_fast",
  "formula_expression": "PEN-FAST = five_or_fewer_years_ago (true 2) + anaphylaxis_angioedema_or_scar (true 2) + treatment_required (true 1); Trubiano 2020; max 5; 0 very_low, 1-2 low, 3 moderate, 4-5 high; low_risk_for_testing iff score < 3",
  "max_score": 5,
  "score": 0,
  "risk": "very_low",
  "low_risk_for_testing": true
}

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_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

Centor and McIsaac scores — Compute the Centor score or the McIsaac age-modified score from four caller-assigned pharyngitis findings. The edition is required.
FeverPAIN — Sum the five Little 2013 FeverPAIN flags for sore throat and return the published 0-1 / 2-3 / 4-5 score group.

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.