# NAFLD activity score

NAS

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

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

## What it computes

Return the Kleiner 2005 NAFLD activity score (NAS) as the sum of three caller-assigned integer components (steatosis 0-3, lobular_inflammation 0-3, ballooning 0-2). Max 8. Does not return NASH diagnostic bands.

## When to use

When an agent already has Kleiner 2005 NAS component points and needs the published total. magent does not read histology or assign grades from a narrative, and does not apply NASH diagnostic cutoffs.

## When not to use

- Not a medical device and not a NASH diagnosis, biopsy, or treatment order. magent does not read histology.
- Inputs are caller-assigned Kleiner 2005 point integers (steatosis 0-3, lobular_inflammation 0-3, ballooning 0-2), not percent fat, foci counts, or a fibrosis stage. Paper bins: steatosis <5% / 5–33% / >33–66% / >66%; lobular inflammation none / <2 foci per 200× / 2–4 / >4; ballooning none / few / many or prominent.
- Kleiner 2005 stages fibrosis separately. Fibrosis is not in NAS and is not an input to this tool.
- Kleiner 2005 reported NAS ≥5 correlated with NASH in that study; that is not a diagnostic algorithm. magent returns score and max_score only and does not apply NASH diagnostic bands.

## Formula

```
NAS = steatosis (integer 0-3) + lobular_inflammation (integer 0-3) + ballooning (integer 0-2); Kleiner 2005 caller-assigned; max 8; fibrosis is not in NAS; no NASH diagnostic bands
```

## Citation

[Design and validation of a histological scoring system for nonalcoholic fatty liver disease.](https://doi.org/10.1002/hep.20701)
Kleiner DE, Brunt EM, Van Natta M, et al.
Hepatology. 2005;41(6):1313-1321
DOI: [10.1002/hep.20701](https://doi.org/10.1002/hep.20701)

## Worked example

### All zeros

Given: `ballooning=0, lobular_inflammation=0, steatosis=0`

1. steatosis 0 + lobular_inflammation 0 + ballooning 0
2. Score = 0 (max 8). No NASH band.


### Maximum published score

Given: `ballooning=2, lobular_inflammation=3, steatosis=3`

1. steatosis 3 + lobular_inflammation 3 + ballooning 2
2. Score = 8 (max 8). No NASH band.


## Also searched as

- NAFLD activity score
- NAS
- Kleiner NAS
- Kleiner 2005 NAS
- NASH CRN NAS
- NAFLD Activity Score
- NAS histology score
- Kleiner NAFLD activity score

## Parameters

- `steatosis` (integer, required): Caller-assigned Kleiner 2005 steatosis points 0-3 (paper bins: 0 <5%; 1 5–33%; 2 >33–66%; 3 >66%). magent does not read histology.
- `lobular_inflammation` (integer, required): Caller-assigned Kleiner 2005 lobular inflammation points 0-3 (paper bins: 0 none; 1 <2 foci/200×; 2 2–4 foci/200×; 3 >4 foci/200×). magent does not read histology.
- `ballooning` (integer, required): Caller-assigned Kleiner 2005 hepatocellular ballooning points 0-2 (paper bins: 0 none; 1 few; 2 many/prominent). magent does not read histology.

## 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/nafld_nas`
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": [
    {
      "ballooning": "0",
      "lobular_inflammation": "0",
      "steatosis": "0"
    },
    {
      "ballooning": "0",
      "lobular_inflammation": "0",
      "steatosis": "0"
    }
  ]
}
```

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

Example 200:

```json
{
  "count": 2,
  "path": "/api/calc/nafld_nas",
  "items": [
    {
      "components": [
        {
          "value": 0,
          "factor": "steatosis",
          "points": 0,
          "present": true
        },
        {
          "value": 0,
          "factor": "lobular_inflammation",
          "points": 0,
          "present": true
        },
        {
          "value": 0,
          "factor": "ballooning",
          "points": 0,
          "present": 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": "Kleiner DE, Brunt EM, Van Natta M, et al.",
        "doi": "10.1002/hep.20701",
        "id": "kleiner-2005",
        "pmid": "15915461",
        "source": "Hepatology. 2005;41(6):1313-1321",
        "title": "Design and validation of a histological scoring system for nonalcoholic fatty liver disease."
      },
      "formula": "nafld_nas",
      "formula_expression": "NAS = steatosis (integer 0-3) + lobular_inflammation (integer 0-3) + ballooning (integer 0-2); Kleiner 2005 caller-assigned; max 8; fibrosis is not in NAS; no NASH diagnostic bands",
      "max_score": 8,
      "score": 0,
      "ballooning": 0,
      "lobular_inflammation": 0,
      "steatosis": 0
    },
    {
      "components": [
        {
          "value": 0,
          "factor": "steatosis",
          "points": 0,
          "present": true
        },
        {
          "value": 0,
          "factor": "lobular_inflammation",
          "points": 0,
          "present": true
        },
        {
          "value": 0,
          "factor": "ballooning",
          "points": 0,
          "present": 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": "Kleiner DE, Brunt EM, Van Natta M, et al.",
        "doi": "10.1002/hep.20701",
        "id": "kleiner-2005",
        "pmid": "15915461",
        "source": "Hepatology. 2005;41(6):1313-1321",
        "title": "Design and validation of a histological scoring system for nonalcoholic fatty liver disease."
      },
      "formula": "nafld_nas",
      "formula_expression": "NAS = steatosis (integer 0-3) + lobular_inflammation (integer 0-3) + ballooning (integer 0-2); Kleiner 2005 caller-assigned; max 8; fibrosis is not in NAS; no NASH diagnostic bands",
      "max_score": 8,
      "score": 0,
      "ballooning": 0,
      "lobular_inflammation": 0,
      "steatosis": 0
    }
  ]
}
```

## Response fields

- `formula` (string): nafld_nas
- `formula_expression` (string): Exact expression used
- `score` (integer): Kleiner 2005 NAS points 0-8
- `max_score` (integer): Always 8
- `steatosis` (integer): Caller-assigned steatosis points 0-3
- `lobular_inflammation` (integer): Caller-assigned lobular inflammation points 0-3
- `ballooning` (integer): Caller-assigned ballooning points 0-2
- `components` (array): Per-component caller-assigned points
- `citation` (object): Kleiner et al. Hepatology 2005 citation
- `disclaimer` (string): Not a medical device

## Example JSON

Frozen fixture. Not a live lookup.

```json
{
  "components": [
    {
      "value": 0,
      "factor": "steatosis",
      "points": 0,
      "present": true
    },
    {
      "value": 0,
      "factor": "lobular_inflammation",
      "points": 0,
      "present": true
    },
    {
      "value": 0,
      "factor": "ballooning",
      "points": 0,
      "present": 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": "Kleiner DE, Brunt EM, Van Natta M, et al.",
    "doi": "10.1002/hep.20701",
    "id": "kleiner-2005",
    "pmid": "15915461",
    "source": "Hepatology. 2005;41(6):1313-1321",
    "title": "Design and validation of a histological scoring system for nonalcoholic fatty liver disease."
  },
  "formula": "nafld_nas",
  "formula_expression": "NAS = steatosis (integer 0-3) + lobular_inflammation (integer 0-3) + ballooning (integer 0-2); Kleiner 2005 caller-assigned; max 8; fibrosis is not in NAS; no NASH diagnostic bands",
  "max_score": 8,
  "score": 0,
  "ballooning": 0,
  "lobular_inflammation": 0,
  "steatosis": 0
}
```

## Errors

- HTTP 400 `invalid_nafld_nas`: steatosis must be an integer 0-3, lobular_inflammation an integer 0-3, and ballooning an integer 0-2 (Kleiner 2005 NAS). 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

- [FIB-4](https://magentlab.com/docs/fib4) — Compute the FIB-4 fibrosis index from age, AST, ALT, and platelets.
- [NAFLD fibrosis score](https://magentlab.com/docs/nafld-fibrosis) — Compute the Angulo 2007 NAFLD fibrosis score from age, BMI, IFG/diabetes, AST, ALT, platelets, and albumin.
- [BARD](https://magentlab.com/docs/bard) — Sum the Harrison 2008 BARD score (BMI ≥28, AST/ALT ≥0.8, diabetes) and return low (0–1) or high (2–4).
- [SAFE score](https://magentlab.com/docs/safe) — Compute the Sripongpun 2023 steatosis-associated fibrosis estimator (SAFE) from age, caller-supplied BMI, diabetes, AST, ALT, globulin in g/dL, and platelets.

## 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.