# Nutritional Risk Index (NRI)

NRI

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

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

## What it computes

Apply the VA TPN Cooperative Study 1991 Nutritional Risk Index from caller-supplied albumin and current/usual weight.

## When to use

When an agent has serum albumin and current and usual weights and needs the published VA TPN 1991 NRI screening and strata, not GNRI, not PNI, and not a malnutrition diagnosis or TPN order.

## When not to use

- Not a medical device. magent does not assay albumin or weigh the patient.
- Not a malnutrition diagnosis or TPN order.
- VA TPN 1991 NRI only. This is not GNRI and not PNI.

## Formula

```
NRI = 1.519 × albumin_g_l + 0.417 × (current_weight_kg / usual_weight_kg) × 100
```

## Citation

[Perioperative total parenteral nutrition in surgical patients](https://doi.org/10.1056/NEJM199108223250801)
The Veterans Affairs Total Parenteral Nutrition Cooperative Study Group
N Engl J Med. 1991;325(8):525-532
DOI: [10.1056/NEJM199108223250801](https://doi.org/10.1056/NEJM199108223250801)

## Worked example

### Albumin 40 g/L, current 70 kg, usual 70 kg

Given: `albumin_g_l=40, current_weight_kg=70, usual_weight_kg=70`

1. NRI = 1.519 × 40 + 41.7 × (70 / 70) = 60.76 + 41.7 = 102.46 → 102.5
2. 102.5 > 100 → not_malnourished


### Albumin 38.38 g/L, current 70 kg, usual 70 kg

Given: `albumin_g_l=38.38, current_weight_kg=70, usual_weight_kg=70`

1. NRI = 1.519 × 38.38 + 41.7 × (70 / 70) = 58.29922 + 41.7 = 99.99922 → 100.0
2. 100.0 ≤ 100 → screening malnourished
3. 97.5 < 100.0 ≤ 100 → borderline_malnourished


## Also searched as

- Nutritional Risk Index
- NRI
- VA TPN NRI
- Veterans Affairs NRI
- perioperative TPN nutrition index
- serum albumin usual weight NRI
- NEJM 1991 NRI

## Parameters

- `albumin_g_l` (number, optional): Serum albumin in g/L (10-60). Provide this or albumin_g_dl, not both. VA TPN 1991 NRI uses g/L. magent does not assay albumin.
- `albumin_g_dl` (number, optional): Serum albumin in g/dL (1-6). Converted as g/L = g/dL × 10. Provide this or albumin_g_l, not both.
- `current_weight_kg` (number, required): Current weight in kg (1-500). Not capped at usual weight. magent does not weigh the patient.
- `usual_weight_kg` (number, required): Usual weight in kg (1-500). Must be greater than 0. magent does not weigh the patient.

## 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/nri`
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_g_l": "40",
      "current_weight_kg": "70",
      "usual_weight_kg": "70"
    },
    {
      "albumin_g_l": "40",
      "current_weight_kg": "70",
      "usual_weight_kg": "70"
    }
  ]
}
```

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

Example 200:

```json
{
  "count": 2,
  "path": "/api/calc/nri",
  "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": "The Veterans Affairs Total Parenteral Nutrition Cooperative Study Group",
        "doi": "10.1056/NEJM199108223250801",
        "id": "va-tpn-1991",
        "pmid": "1906163",
        "source": "N Engl J Med. 1991;325(8):525-532",
        "title": "Perioperative total parenteral nutrition in surgical patients"
      },
      "formula": "nri",
      "formula_expression": "NRI = 1.519 × albumin_g_l + 0.417 × (current_weight_kg / usual_weight_kg) × 100",
      "albumin_g_l": 40.0,
      "current_weight_kg": 70.0,
      "nri": 102.5,
      "screening": "not_malnourished",
      "stratification": "not_malnourished",
      "usual_weight_kg": 70.0
    },
    {
      "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": "The Veterans Affairs Total Parenteral Nutrition Cooperative Study Group",
        "doi": "10.1056/NEJM199108223250801",
        "id": "va-tpn-1991",
        "pmid": "1906163",
        "source": "N Engl J Med. 1991;325(8):525-532",
        "title": "Perioperative total parenteral nutrition in surgical patients"
      },
      "formula": "nri",
      "formula_expression": "NRI = 1.519 × albumin_g_l + 0.417 × (current_weight_kg / usual_weight_kg) × 100",
      "albumin_g_l": 40.0,
      "current_weight_kg": 70.0,
      "nri": 102.5,
      "screening": "not_malnourished",
      "stratification": "not_malnourished",
      "usual_weight_kg": 70.0
    }
  ]
}
```

## Response fields

- `formula` (string): nri
- `formula_expression` (string): VA TPN 1991 NRI expression in g/L and kg
- `albumin_g_l` (number): Serum albumin used in g/L (after g/dL conversion when supplied)
- `current_weight_kg` (number): Current weight used in kg (not capped at usual weight)
- `usual_weight_kg` (number): Usual weight used in kg
- `nri` (number): Nutritional Risk Index, 1 decimal
- `screening` (string): malnourished if NRI ≤ 100; not_malnourished if NRI > 100 (VA TPN 1991)
- `stratification` (string): not_malnourished if NRI > 100; borderline_malnourished if 97.5 < NRI ≤ 100; mildly_malnourished if 83.5 ≤ NRI ≤ 97.5; severely_malnourished if NRI < 83.5
- `citation` (object): VA TPN Cooperative Study 1991 NEJM 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": "The Veterans Affairs Total Parenteral Nutrition Cooperative Study Group",
    "doi": "10.1056/NEJM199108223250801",
    "id": "va-tpn-1991",
    "pmid": "1906163",
    "source": "N Engl J Med. 1991;325(8):525-532",
    "title": "Perioperative total parenteral nutrition in surgical patients"
  },
  "formula": "nri",
  "formula_expression": "NRI = 1.519 × albumin_g_l + 0.417 × (current_weight_kg / usual_weight_kg) × 100",
  "albumin_g_l": 40.0,
  "current_weight_kg": 70.0,
  "nri": 102.5,
  "screening": "not_malnourished",
  "stratification": "not_malnourished",
  "usual_weight_kg": 70.0
}
```

## Errors

- HTTP 400 `invalid_albumin`: albumin_g_dl (1-6) or albumin_g_l (10-60) is required Returned before settlement; you are not charged.
- HTTP 400 `invalid_weight`: weight_kg (1-500) or weight_lb (2-1100) is required Returned before settlement; you are not charged.
- HTTP 400 `invalid_usual_weight`: usual_weight_kg must be a number from 1 to 500 (VA TPN 1991 NRI). 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

- [Charlson CCI](https://magentlab.com/docs/charlson) — Sum the nineteen Charlson 1987 original comorbidity weights and return the published 1-year mortality group.
- [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.

## 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.