# R factor

R factor

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

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

## What it computes

Compute the Bénichou 1990 / CIOMS R ratio from ALT, ALP, and their laboratory upper limits of normal, then classify hepatocellular (R ≥ 5), cholestatic (R ≤ 2), or mixed (2 < R < 5).

## When to use

When an agent needs the published CIOMS enzyme pattern from ALT and ALP and must not invent a RUCAM causality score or a DILI diagnosis.

## When not to use

- Not a medical device. Not a DILI diagnosis or causality assessment.
- magent does not assay enzymes. Caller supplies ALT, ALP, and laboratory ULNs.
- R is the enzyme pattern only (hepatocellular, cholestatic, or mixed). magent does not compute RUCAM causality points.

## Formula

```
R = (ALT / ALT_ULN) / (ALP / ALP_ULN)
```

## Citation

[Criteria of drug-induced liver disorders. Report of an international consensus meeting](https://doi.org/10.1016/0168-8278(90)90124-A)
Bénichou C
J Hepatol. 1990;11(2):272-276
DOI: [10.1016/0168-8278(90)90124-A](https://doi.org/10.1016/0168-8278(90)90124-A)

## Worked example

### ALT 200 U/L (ULN 40), ALP 100 U/L (ULN 100)

Given: `alp_u_l=100, alp_uln_u_l=100, alt_u_l=200, alt_uln_u_l=40`

1. ALT / ALT_ULN = 200 / 40 = 5.0
2. ALP / ALP_ULN = 100 / 100 = 1.0
3. R = 5.0 / 1.0 = 5.0
4. Round R to 1 decimal → 5.0
5. R ≥ 5 → hepatocellular


## Also searched as

- R ratio
- R factor
- CIOMS R
- ALT ALP ratio
- hepatocellular cholestatic mixed
- Bénichou R factor
- drug-induced liver injury pattern
- enzyme pattern R

## Parameters

- `alt_u_l` (number, required): Alanine aminotransferase in U/L (1-10000).
- `alp_u_l` (number, required): Alkaline phosphatase in U/L (1-10000). Must be greater than 0.
- `alt_uln_u_l` (number, required): Laboratory ALT upper limit of normal in U/L (5-200). Required; magent does not assume 40.
- `alp_uln_u_l` (number, required): Laboratory ALP upper limit of normal in U/L (20-500). Required; must be greater than 0.

## 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/r_factor`
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": [
    {
      "alp_u_l": "100",
      "alp_uln_u_l": "100",
      "alt_u_l": "200",
      "alt_uln_u_l": "40"
    },
    {
      "alp_u_l": "100",
      "alp_uln_u_l": "100",
      "alt_u_l": "200",
      "alt_uln_u_l": "40"
    }
  ]
}
```

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

Example 200:

```json
{
  "count": 2,
  "path": "/api/calc/r_factor",
  "items": [
    {
      "pattern": "hepatocellular",
      "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": "Bénichou C",
        "doi": "10.1016/0168-8278(90)90124-A",
        "id": "benichou-1990",
        "pmid": "2254635",
        "source": "J Hepatol. 1990;11(2):272-276",
        "title": "Criteria of drug-induced liver disorders. Report of an international consensus meeting"
      },
      "formula": "r_factor",
      "formula_expression": "R = (ALT / ALT_ULN) / (ALP / ALP_ULN)",
      "alt_u_l": 200.0,
      "alp_u_l": 100.0,
      "alp_uln_u_l": 100.0,
      "alt_uln_u_l": 40.0,
      "r_ratio": 5.0
    },
    {
      "pattern": "hepatocellular",
      "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": "Bénichou C",
        "doi": "10.1016/0168-8278(90)90124-A",
        "id": "benichou-1990",
        "pmid": "2254635",
        "source": "J Hepatol. 1990;11(2):272-276",
        "title": "Criteria of drug-induced liver disorders. Report of an international consensus meeting"
      },
      "formula": "r_factor",
      "formula_expression": "R = (ALT / ALT_ULN) / (ALP / ALP_ULN)",
      "alt_u_l": 200.0,
      "alp_u_l": 100.0,
      "alp_uln_u_l": 100.0,
      "alt_uln_u_l": 40.0,
      "r_ratio": 5.0
    }
  ]
}
```

## Response fields

- `formula` (string): r_factor
- `formula_expression` (string): Exact expression used
- `alt_u_l` (number): ALT in U/L
- `alp_u_l` (number): ALP in U/L
- `alt_uln_u_l` (number): Laboratory ALT upper limit of normal in U/L
- `alp_uln_u_l` (number): Laboratory ALP upper limit of normal in U/L
- `r_ratio` (number): R ratio, 1 decimal
- `pattern` (string): Bénichou 1990 / CIOMS enzyme pattern: hepatocellular (R ≥ 5), cholestatic (R ≤ 2), or mixed (2 < R < 5). Classified after rounding R to 1 decimal.
- `citation` (object): Bénichou 1990 / CIOMS citation
- `disclaimer` (string): Not-a-device notice

## Example JSON

Frozen fixture. Not a live lookup.

```json
{
  "pattern": "hepatocellular",
  "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": "Bénichou C",
    "doi": "10.1016/0168-8278(90)90124-A",
    "id": "benichou-1990",
    "pmid": "2254635",
    "source": "J Hepatol. 1990;11(2):272-276",
    "title": "Criteria of drug-induced liver disorders. Report of an international consensus meeting"
  },
  "formula": "r_factor",
  "formula_expression": "R = (ALT / ALT_ULN) / (ALP / ALP_ULN)",
  "alt_u_l": 200.0,
  "alp_u_l": 100.0,
  "alp_uln_u_l": 100.0,
  "alt_uln_u_l": 40.0,
  "r_ratio": 5.0
}
```

## Errors

- HTTP 400 `invalid_alt`: alt_u_l must be a number from 1 to 10000 Returned before settlement; you are not charged.
- HTTP 400 `invalid_alp`: alp_u_l must be a number from 1 to 10000 (Bénichou 1990). Returned before settlement; you are not charged.
- HTTP 400 `invalid_alt_uln`: alt_uln_u_l must be a number from 5 to 200. Returned before settlement; you are not charged.
- HTTP 400 `invalid_alp_uln`: alp_uln_u_l must be a number from 20 to 500. Returned before settlement; you are not charged.
- HTTP 400 `invalid_r_ratio`: ALP and ALP ULN must be greater than 0 so R is defined (Bénichou 1990). 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

- [ALBI](https://magentlab.com/docs/albi) — Compute the Johnson 2015 albumin-bilirubin (ALBI) linear predictor and grade from total bilirubin and albumin.
- [Child–Pugh](https://magentlab.com/docs/child-pugh) — Compute the Child–Turcotte–Pugh cirrhosis severity score from bilirubin, albumin, INR, encephalopathy, and ascites.
- [FIB-4](https://magentlab.com/docs/fib4) — Compute the FIB-4 fibrosis index from age, AST, ALT, 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.