# Apfel 1999 PONV risk score

Apfel PONV score

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

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

## What it computes

Sum the four Apfel 1999 predictors for postoperative nausea and vomiting and return the published integer score (0-4).

## When to use

When an agent needs the published Apfel 1999 integer score and must not invent a prophylaxis order, a PONV diagnosis, or the paper's incidence percents.

## When not to use

- Not a medical device.
- Not a prophylaxis order and not a diagnosis of PONV.
- Apfel 1999 reported incidences by score. This tool returns the integer score without those percents.
- The caller assigns sex, motion-sickness or PONV history, smoking status, and the postoperative opioid plan. magent does not take an anesthetic.

## Formula

```
Apfel = female + history_motion_sickness_or_ponv + nonsmoker + postoperative_opioids; each 1 if true; max 4
```

## Citation

[A simplified risk score for predicting postoperative nausea and vomiting: conclusions from cross-validations between two centers.](https://doi.org/10.1097/00000542-199909000-00022)
Apfel CC, Läärä E, Koivuranta M, Greim CA, Roewer N
Anesthesiology. 1999;91(3):693-700
DOI: [10.1097/00000542-199909000-00022](https://doi.org/10.1097/00000542-199909000-00022)

## Worked example

### Male, no history, smoker, no postoperative opioids

Given: `history_motion_sickness_or_ponv=false, nonsmoker=false, postoperative_opioids=false, sex=male`

1. Male → 0; history absent → 0; nonsmoker false → 0; postoperative opioids false → 0
2. Score = 0 (max 4); band 0


### Female, history, nonsmoker, postoperative opioids

Given: `history_motion_sickness_or_ponv=true, nonsmoker=true, postoperative_opioids=true, sex=female`

1. Female → 1; history present → 1; nonsmoker → 1; postoperative opioids → 1
2. Score = 4 (max 4); band 4


## Also searched as

- Apfel score
- Apfel PONV score
- Apfel 1999
- postoperative nausea and vomiting score
- simplified PONV risk score
- PONV predictors Apfel
- motion sickness PONV score

## Parameters

- `sex` (string, required): female or male (Apfel 1999). Female scores 1. Male scores 0. Assigned by the caller.
- `history_motion_sickness_or_ponv` (boolean, required): History of motion sickness or postoperative nausea and vomiting (Apfel 1999). true or false as assigned by the caller. 1 point if true.
- `nonsmoker` (boolean, required): Nonsmoking status (Apfel 1999). true scores 1. Smokers (false) score 0. Assigned by the caller.
- `postoperative_opioids` (boolean, required): Postoperative opioids planned or given (Apfel 1999). true or false as assigned by the caller. 1 point if true. magent does not take an anesthetic.

## 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/apfel`
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": [
    {
      "history_motion_sickness_or_ponv": "false",
      "nonsmoker": "false",
      "postoperative_opioids": "false",
      "sex": "male"
    },
    {
      "history_motion_sickness_or_ponv": "false",
      "nonsmoker": "false",
      "postoperative_opioids": "false",
      "sex": "male"
    }
  ]
}
```

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

Example 200:

```json
{
  "count": 2,
  "path": "/api/calc/apfel",
  "items": [
    {
      "band": "0",
      "components": [
        {
          "factor": "female",
          "points": 0,
          "present": false
        },
        {
          "factor": "history_motion_sickness_or_ponv",
          "points": 0,
          "present": false
        },
        {
          "factor": "nonsmoker",
          "points": 0,
          "present": false
        },
        {
          "factor": "postoperative_opioids",
          "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": "Apfel CC, Läärä E, Koivuranta M, Greim CA, Roewer N",
        "doi": "10.1097/00000542-199909000-00022",
        "id": "apfel-1999",
        "pmid": "10485781",
        "source": "Anesthesiology. 1999;91(3):693-700",
        "title": "A simplified risk score for predicting postoperative nausea and vomiting: conclusions from cross-validations between two centers."
      },
      "formula": "apfel",
      "formula_expression": "Apfel = female + history_motion_sickness_or_ponv + nonsmoker + postoperative_opioids; each 1 if true; max 4",
      "max_score": 4,
      "score": 0,
      "sex": "male"
    },
    {
      "band": "0",
      "components": [
        {
          "factor": "female",
          "points": 0,
          "present": false
        },
        {
          "factor": "history_motion_sickness_or_ponv",
          "points": 0,
          "present": false
        },
        {
          "factor": "nonsmoker",
          "points": 0,
          "present": false
        },
        {
          "factor": "postoperative_opioids",
          "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": "Apfel CC, Läärä E, Koivuranta M, Greim CA, Roewer N",
        "doi": "10.1097/00000542-199909000-00022",
        "id": "apfel-1999",
        "pmid": "10485781",
        "source": "Anesthesiology. 1999;91(3):693-700",
        "title": "A simplified risk score for predicting postoperative nausea and vomiting: conclusions from cross-validations between two centers."
      },
      "formula": "apfel",
      "formula_expression": "Apfel = female + history_motion_sickness_or_ponv + nonsmoker + postoperative_opioids; each 1 if true; max 4",
      "max_score": 4,
      "score": 0,
      "sex": "male"
    }
  ]
}
```

## Response fields

- `formula` (string): apfel
- `formula_expression` (string): Exact expression used
- `score` (integer): Apfel 1999 points 0-4
- `max_score` (integer): 4
- `band` (string): Published Apfel 1999 score stratum as a string: 0, 1, 2, 3, or 4. The integer score, not a prophylaxis order. Percents are not returned.
- `sex` (string): female or male
- `components` (array): Per-predictor points
- `citation` (object): Apfel et al. Anesthesiology 1999 citation
- `disclaimer` (string): Not-a-device notice

## Example JSON

Frozen fixture. Not a live lookup.

```json
{
  "band": "0",
  "components": [
    {
      "factor": "female",
      "points": 0,
      "present": false
    },
    {
      "factor": "history_motion_sickness_or_ponv",
      "points": 0,
      "present": false
    },
    {
      "factor": "nonsmoker",
      "points": 0,
      "present": false
    },
    {
      "factor": "postoperative_opioids",
      "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": "Apfel CC, Läärä E, Koivuranta M, Greim CA, Roewer N",
    "doi": "10.1097/00000542-199909000-00022",
    "id": "apfel-1999",
    "pmid": "10485781",
    "source": "Anesthesiology. 1999;91(3):693-700",
    "title": "A simplified risk score for predicting postoperative nausea and vomiting: conclusions from cross-validations between two centers."
  },
  "formula": "apfel",
  "formula_expression": "Apfel = female + history_motion_sickness_or_ponv + nonsmoker + postoperative_opioids; each 1 if true; max 4",
  "max_score": 4,
  "score": 0,
  "sex": "male"
}
```

## Errors

- HTTP 400 `invalid_sex`: sex must be female or male 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

- [Surgical Apgar](https://magentlab.com/docs/surgical-apgar) — Compute the Gawande 2007 intraoperative Surgical Apgar score from estimated blood loss, lowest mean arterial pressure, and lowest heart rate.
- [COWS](https://magentlab.com/docs/cows) — Sum the eleven Wesson 2003 Clinical Opiate Withdrawal Scale (COWS) items from caller-assigned appendix integers and return the published total (max 48) with the published severity cutoffs.

## 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 echoing accepted, payload, and extensions when present).
- 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.
- 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.