# PONS perioperative nutrition screen

PONS

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

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

## What it computes

Sum the four Wischmeyer 2018 Perioperative Nutrition Screen (PONS) flags and return whether any item is positive (high nutritional risk).

## When to use

When an agent has caller-assigned Wischmeyer 2018 PONS questions and needs the published point total and high-risk flag, not a diet order, not a malnutrition diagnosis, and without computing BMI or assaying albumin.

## When not to use

- Not a medical device.
- Not a diet order or malnutrition diagnosis.
- magent does not weigh the patient, compute BMI, or assay albumin. The caller assigns each flag. magent does not take height, weight, age, or albumin as numeric inputs.
- Albumin cutoff is <3.0 g/dL (Wischmeyer 2018), not 3 g/L.
- This is not NRS-2002, not NUTRIC, and not MUST.

## Formula

```
PONS = bmi_low + weight_loss_gt_10pct_6mo + oral_intake_reduced_gt_50pct_week + albumin_lt_3_g_dl; each 1 if true; max 4; high_risk iff score ≥ 1
```

## Citation

[American Society for Enhanced Recovery and Perioperative Quality Initiative Joint Consensus Statement on Nutrition Screening and Therapy Within a Surgical Enhanced Recovery Pathway](https://doi.org/10.1213/ANE.0000000000002743)
Wischmeyer PE, Carli F, Evans DC, et al.
Anesth Analg. 2018;126(6):1883-1895
DOI: [10.1213/ANE.0000000000002743](https://doi.org/10.1213/ANE.0000000000002743)

## Worked example

### All four false

Given: `albumin_lt_3_g_dl=false, bmi_low=false, oral_intake_reduced_gt_50pct_week=false, weight_loss_gt_10pct_6mo=false`

1. score = 0 (max 4)
2. high_risk false


### Low BMI only

Given: `albumin_lt_3_g_dl=false, bmi_low=true, oral_intake_reduced_gt_50pct_week=false, weight_loss_gt_10pct_6mo=false`

1. score = 1 (max 4)
2. high_risk true (any positive screen)


### All four true

Given: `albumin_lt_3_g_dl=true, bmi_low=true, oral_intake_reduced_gt_50pct_week=true, weight_loss_gt_10pct_6mo=true`

1. score = 4 (max 4)
2. high_risk true


## Also searched as

- PONS
- Perioperative Nutrition Screen
- Wischmeyer PONS
- perioperative nutrition screening
- PONS score
- surgical nutrition screen
- PONS questionnaire

## Parameters

- `bmi_low` (boolean, required): Caller-assigned Wischmeyer 2018 PONS low-BMI flag: BMI <18.5 kg/m² if age ≤65, or BMI <20 kg/m² if age >65. true or false. magent does not take age, weigh the patient, or compute BMI.
- `weight_loss_gt_10pct_6mo` (boolean, required): Caller-assigned Wischmeyer 2018 PONS flag: weight loss >10% in the past 6 months. true or false. magent does not weigh the patient.
- `oral_intake_reduced_gt_50pct_week` (boolean, required): Caller-assigned Wischmeyer 2018 PONS flag: reduced oral intake by >50% in the past week. true or false. magent does not measure intake.
- `albumin_lt_3_g_dl` (boolean, required): Caller-assigned Wischmeyer 2018 PONS flag: preoperative serum albumin <3.0 g/dL (not 3 g/L). true or false. magent does not assay albumin.

## 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/pons`
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": [
    {
      "albumin_lt_3_g_dl": "false",
      "bmi_low": "false",
      "oral_intake_reduced_gt_50pct_week": "false",
      "weight_loss_gt_10pct_6mo": "false"
    },
    {
      "albumin_lt_3_g_dl": "false",
      "bmi_low": "false",
      "oral_intake_reduced_gt_50pct_week": "false",
      "weight_loss_gt_10pct_6mo": "false"
    }
  ]
}
```

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

Example 200:

```json
{
  "count": 2,
  "path": "/api/calc/pons",
  "items": [
    {
      "components": [
        {
          "factor": "bmi_low",
          "points": 0,
          "present": false
        },
        {
          "factor": "weight_loss_gt_10pct_6mo",
          "points": 0,
          "present": false
        },
        {
          "factor": "oral_intake_reduced_gt_50pct_week",
          "points": 0,
          "present": false
        },
        {
          "factor": "albumin_lt_3_g_dl",
          "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": "Wischmeyer PE, Carli F, Evans DC, et al.",
        "doi": "10.1213/ANE.0000000000002743",
        "id": "wischmeyer-2018",
        "pmid": "29369092",
        "source": "Anesth Analg. 2018;126(6):1883-1895",
        "title": "American Society for Enhanced Recovery and Perioperative Quality Initiative Joint Consensus Statement on Nutrition Screening and Therapy Within a Surgical Enhanced Recovery Pathway"
      },
      "formula": "pons",
      "formula_expression": "PONS = bmi_low + weight_loss_gt_10pct_6mo + oral_intake_reduced_gt_50pct_week + albumin_lt_3_g_dl; each 1 if true; max 4; high_risk iff score ≥ 1",
      "max_score": 4,
      "score": 0,
      "high_risk": false
    },
    {
      "components": [
        {
          "factor": "bmi_low",
          "points": 0,
          "present": false
        },
        {
          "factor": "weight_loss_gt_10pct_6mo",
          "points": 0,
          "present": false
        },
        {
          "factor": "oral_intake_reduced_gt_50pct_week",
          "points": 0,
          "present": false
        },
        {
          "factor": "albumin_lt_3_g_dl",
          "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": "Wischmeyer PE, Carli F, Evans DC, et al.",
        "doi": "10.1213/ANE.0000000000002743",
        "id": "wischmeyer-2018",
        "pmid": "29369092",
        "source": "Anesth Analg. 2018;126(6):1883-1895",
        "title": "American Society for Enhanced Recovery and Perioperative Quality Initiative Joint Consensus Statement on Nutrition Screening and Therapy Within a Surgical Enhanced Recovery Pathway"
      },
      "formula": "pons",
      "formula_expression": "PONS = bmi_low + weight_loss_gt_10pct_6mo + oral_intake_reduced_gt_50pct_week + albumin_lt_3_g_dl; each 1 if true; max 4; high_risk iff score ≥ 1",
      "max_score": 4,
      "score": 0,
      "high_risk": false
    }
  ]
}
```

## Response fields

- `formula` (string): pons
- `formula_expression` (string): Exact expression used
- `score` (integer): PONS points 0-4
- `max_score` (integer): 4
- `high_risk` (boolean): true iff score ≥ 1 (Wischmeyer 2018: any positive PONS screen). Not a diet order or malnutrition diagnosis.
- `components` (array): Per-item points
- `citation` (object): Wischmeyer et al. Anesth Analg 2018 citation
- `disclaimer` (string): Not-a-device notice

## Example JSON

Frozen fixture. Not a live lookup.

```json
{
  "components": [
    {
      "factor": "bmi_low",
      "points": 0,
      "present": false
    },
    {
      "factor": "weight_loss_gt_10pct_6mo",
      "points": 0,
      "present": false
    },
    {
      "factor": "oral_intake_reduced_gt_50pct_week",
      "points": 0,
      "present": false
    },
    {
      "factor": "albumin_lt_3_g_dl",
      "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": "Wischmeyer PE, Carli F, Evans DC, et al.",
    "doi": "10.1213/ANE.0000000000002743",
    "id": "wischmeyer-2018",
    "pmid": "29369092",
    "source": "Anesth Analg. 2018;126(6):1883-1895",
    "title": "American Society for Enhanced Recovery and Perioperative Quality Initiative Joint Consensus Statement on Nutrition Screening and Therapy Within a Surgical Enhanced Recovery Pathway"
  },
  "formula": "pons",
  "formula_expression": "PONS = bmi_low + weight_loss_gt_10pct_6mo + oral_intake_reduced_gt_50pct_week + albumin_lt_3_g_dl; each 1 if true; max 4; high_risk iff score ≥ 1",
  "max_score": 4,
  "score": 0,
  "high_risk": false
}
```

## Errors

- 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

- [NRS-2002](https://magentlab.com/docs/nrs-2002) — Sum Kondrup 2003 NRS-2002 impaired nutritional status (0–3), disease severity (0–3), and 1 if age ≥70, and return whether the total is at nutritional risk (score ≥3).
- [NUTRIC](https://magentlab.com/docs/nutric) — Sum Heyland 2011 original 6-variable NUTRIC (Nutrition Risk in the Critically Ill) Table 4 overall points, including IL-6, and return whether the total is high nutrition risk (score ≥6).
- [MUST](https://magentlab.com/docs/must) — Sum Stratton 2004 MUST (BMI, unplanned weight-loss percent, and acute disease with no nutritional intake >5 days) and return score 0–6 with risk low, medium, or high.

## 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.