# RIPASA score

RIPASA score

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

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

## What it computes

Sum the Chong 2010 RIPASA points from 15 caller-assigned findings and return below_cutoff (<7.5) or at_or_above_cutoff (≥7.5) from the derivation ROC only.

## When to use

When an agent needs the published Chong 2010 RIPASA total and must not invent abdominal findings, laboratory cutoffs, identity-card status, an appendicitis diagnosis, or an operating-room protocol.

## When not to use

- Not a medical device. Not an appendicitis diagnosis or operating-room protocol.
- Fever, raised WCC, and foreign NRIC are caller-assigned flags. magent does not apply a temperature or WBC cutoff and does not read identity documents.
- Findings are caller-assigned. magent does not examine the abdomen.
- Bands are the Chong 2010 derivation ROC cutoff only (<7.5 below_cutoff; ≥7.5 at_or_above_cutoff). magent does not add probable or possible labels from later papers.

## Formula

```
RIPASA = (age<40 → 1.0; age≥40 → 0.5) + (male 1.0; female 0.5) + 0.5*rif_pain + 0.5*migration_to_rif + nausea_vomiting + anorexia + (symptoms_lt_48h 1.0; else 0.5) + rif_tenderness + 2*guarding + rebound_tenderness + 2*rovsing_sign + fever + raised_wcc + negative_urinalysis + foreign_nric; Chong 2010; max 16; <7.5 below_cutoff, ≥7.5 at_or_above_cutoff
```

## Citation

[Development of the RIPASA score: a new appendicitis scoring system for the diagnosis of acute appendicitis](https://pubmed.ncbi.nlm.nih.gov/20428744)
Chong CF, Adi MIW, Thien A, Suyoi A, Mackie AJ, Tin AS, Tripathi S, Jaman NH, Tan KK, Kok KY, Mathew VV, Paw O, Chua HB, Yapp SK
Singapore Med J. 2010;51(3):220-225
DOI: none

## Worked example

### Age 50, female, all flags false, symptoms 48h or longer

Given: `age=50, anorexia=false, fever=false, foreign_nric=false, guarding=false, migration_to_rif=false, nausea_vomiting=false, negative_urinalysis=false, raised_wcc=false, rebound_tenderness=false, rif_pain=false, rif_tenderness=false, rovsing_sign=false, sex=female, symptoms_lt_48h=false`

1. Age 50 ≥40 → 0.5; female → 0.5; symptoms_lt_48h false → 0.5; remaining flags false → 0
2. Score = 1.5 (max 16); ripasa_band = below_cutoff (<7.5)


### Derivation ROC cutoff 7.5

Given: `age=50, anorexia=true, fever=false, foreign_nric=false, guarding=true, migration_to_rif=false, nausea_vomiting=true, negative_urinalysis=false, raised_wcc=false, rebound_tenderness=false, rif_pain=false, rif_tenderness=false, rovsing_sign=true, sex=female, symptoms_lt_48h=false`

1. Baseline 1.5 + nausea_vomiting 1 + anorexia 1 + guarding 2 + rovsing_sign 2
2. Score = 7.5 (max 16); ripasa_band = at_or_above_cutoff (≥7.5)


## Also searched as

- RIPASA score
- RIPASA appendicitis
- Chong 2010
- Raja Isteri Pengiran Anak Saleha
- appendicitis scoring system
- RIPASA
- RIF appendicitis score
- foreign NRIC appendicitis

## Parameters

- `age` (integer, required): Age in years as an integer from 1 to 120 (Chong 2010). <40 scores 1.0; ≥40 scores 0.5 (age 40 is the ≥40 arm). magent does not assign age.
- `sex` (string, required): Caller-assigned sex (Chong 2010). male scores 1.0; female scores 0.5. magent does not assign sex.
- `rif_pain` (boolean, required): Pain in the right iliac fossa (Chong 2010). true scores 0.5. magent does not take a history.
- `migration_to_rif` (boolean, required): Migration of pain to the right iliac fossa (Chong 2010). true scores 0.5. magent does not take a history.
- `nausea_vomiting` (boolean, required): Nausea or vomiting (Chong 2010). true scores 1.0. magent does not take a history.
- `anorexia` (boolean, required): Anorexia (Chong 2010). true scores 1.0. magent does not take a history.
- `symptoms_lt_48h` (boolean, required): true when symptom duration is under 48 hours (Chong 2010 <48h arm, 1.0). false scores 0.5 (the >48h arm; 48 hours is locked to this arm). magent does not timestamp onset.
- `rif_tenderness` (boolean, required): Right-iliac-fossa tenderness (Chong 2010). true scores 1.0. magent does not examine the abdomen.
- `guarding` (boolean, required): Guarding (Chong 2010). true scores 2.0. magent does not examine the abdomen.
- `rebound_tenderness` (boolean, required): Rebound tenderness (Chong 2010). true scores 1.0. magent does not examine the abdomen.
- `rovsing_sign` (boolean, required): Rovsing sign (Chong 2010). true scores 2.0. magent does not examine the abdomen.
- `fever` (boolean, required): Caller-assigned fever flag (Chong 2010). true scores 1.0. magent does not apply a °C cutoff.
- `raised_wcc` (boolean, required): Caller-assigned raised white-cell-count flag (Chong 2010). true scores 1.0. magent does not apply a WBC cutoff.
- `negative_urinalysis` (boolean, required): Negative urinalysis (Chong 2010). true scores 1.0. magent does not assay urine.
- `foreign_nric` (boolean, required): Caller-assigned foreign national registration identity card item (Chong 2010). true scores 1.0. magent does not read identity documents.

## 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/ripasa`
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": [
    {
      "age": "50",
      "anorexia": "false",
      "fever": "false",
      "foreign_nric": "false",
      "guarding": "false",
      "migration_to_rif": "false",
      "nausea_vomiting": "false",
      "negative_urinalysis": "false",
      "raised_wcc": "false",
      "rebound_tenderness": "false",
      "rif_pain": "false",
      "rif_tenderness": "false",
      "rovsing_sign": "false",
      "sex": "female",
      "symptoms_lt_48h": "false"
    },
    {
      "age": "50",
      "anorexia": "false",
      "fever": "false",
      "foreign_nric": "false",
      "guarding": "false",
      "migration_to_rif": "false",
      "nausea_vomiting": "false",
      "negative_urinalysis": "false",
      "raised_wcc": "false",
      "rebound_tenderness": "false",
      "rif_pain": "false",
      "rif_tenderness": "false",
      "rovsing_sign": "false",
      "sex": "female",
      "symptoms_lt_48h": "false"
    }
  ]
}
```

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

Example 200:

```json
{
  "count": 2,
  "path": "/api/calc/ripasa",
  "items": [
    {
      "components": [
        {
          "value": 50,
          "factor": "age",
          "points": 0.5,
          "present": true
        },
        {
          "value": "female",
          "factor": "sex",
          "points": 0.5,
          "present": true
        },
        {
          "factor": "rif_pain",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "migration_to_rif",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "nausea_vomiting",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "anorexia",
          "points": 0.0,
          "present": false
        },
        {
          "value": false,
          "factor": "symptoms_lt_48h",
          "points": 0.5,
          "present": true
        },
        {
          "factor": "rif_tenderness",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "guarding",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "rebound_tenderness",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "rovsing_sign",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "fever",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "raised_wcc",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "negative_urinalysis",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "foreign_nric",
          "points": 0.0,
          "present": false
        }
      ],
      "age": 50,
      "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": "Chong CF, Adi MIW, Thien A, Suyoi A, Mackie AJ, Tin AS, Tripathi S, Jaman NH, Tan KK, Kok KY, Mathew VV, Paw O, Chua HB, Yapp SK",
        "id": "chong-2010",
        "pmid": "20428744",
        "source": "Singapore Med J. 2010;51(3):220-225",
        "title": "Development of the RIPASA score: a new appendicitis scoring system for the diagnosis of acute appendicitis"
      },
      "formula": "ripasa",
      "formula_expression": "RIPASA = (age<40 → 1.0; age≥40 → 0.5) + (male 1.0; female 0.5) + 0.5*rif_pain + 0.5*migration_to_rif + nausea_vomiting + anorexia + (symptoms_lt_48h 1.0; else 0.5) + rif_tenderness + 2*guarding + rebound_tenderness + 2*rovsing_sign + fever + raised_wcc + negative_urinalysis + foreign_nric; Chong 2010; max 16; <7.5 below_cutoff, ≥7.5 at_or_above_cutoff",
      "max_score": 16,
      "score": 1.5,
      "sex": "female",
      "ripasa_band": "below_cutoff"
    },
    {
      "components": [
        {
          "value": 50,
          "factor": "age",
          "points": 0.5,
          "present": true
        },
        {
          "value": "female",
          "factor": "sex",
          "points": 0.5,
          "present": true
        },
        {
          "factor": "rif_pain",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "migration_to_rif",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "nausea_vomiting",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "anorexia",
          "points": 0.0,
          "present": false
        },
        {
          "value": false,
          "factor": "symptoms_lt_48h",
          "points": 0.5,
          "present": true
        },
        {
          "factor": "rif_tenderness",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "guarding",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "rebound_tenderness",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "rovsing_sign",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "fever",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "raised_wcc",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "negative_urinalysis",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "foreign_nric",
          "points": 0.0,
          "present": false
        }
      ],
      "age": 50,
      "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": "Chong CF, Adi MIW, Thien A, Suyoi A, Mackie AJ, Tin AS, Tripathi S, Jaman NH, Tan KK, Kok KY, Mathew VV, Paw O, Chua HB, Yapp SK",
        "id": "chong-2010",
        "pmid": "20428744",
        "source": "Singapore Med J. 2010;51(3):220-225",
        "title": "Development of the RIPASA score: a new appendicitis scoring system for the diagnosis of acute appendicitis"
      },
      "formula": "ripasa",
      "formula_expression": "RIPASA = (age<40 → 1.0; age≥40 → 0.5) + (male 1.0; female 0.5) + 0.5*rif_pain + 0.5*migration_to_rif + nausea_vomiting + anorexia + (symptoms_lt_48h 1.0; else 0.5) + rif_tenderness + 2*guarding + rebound_tenderness + 2*rovsing_sign + fever + raised_wcc + negative_urinalysis + foreign_nric; Chong 2010; max 16; <7.5 below_cutoff, ≥7.5 at_or_above_cutoff",
      "max_score": 16,
      "score": 1.5,
      "sex": "female",
      "ripasa_band": "below_cutoff"
    }
  ]
}
```

## Response fields

- `formula` (string): ripasa
- `formula_expression` (string): Exact expression used
- `score` (number): Chong 2010 RIPASA points 0.5-16, 0.5 steps
- `max_score` (integer): Always 16
- `ripasa_band` (string): below_cutoff when score is <7.5, at_or_above_cutoff when score is ≥7.5 (Chong 2010 derivation ROC). Not an appendicitis diagnosis.
- `age` (integer): Age in years used for the <40 / ≥40 split
- `sex` (string): female or male
- `components` (array): Per-factor points
- `citation` (object): Chong 2010 Singapore Med J citation
- `disclaimer` (string): Not-a-device notice

## Example JSON

Frozen fixture. Not a live lookup.

```json
{
  "components": [
    {
      "value": 50,
      "factor": "age",
      "points": 0.5,
      "present": true
    },
    {
      "value": "female",
      "factor": "sex",
      "points": 0.5,
      "present": true
    },
    {
      "factor": "rif_pain",
      "points": 0.0,
      "present": false
    },
    {
      "factor": "migration_to_rif",
      "points": 0.0,
      "present": false
    },
    {
      "factor": "nausea_vomiting",
      "points": 0.0,
      "present": false
    },
    {
      "factor": "anorexia",
      "points": 0.0,
      "present": false
    },
    {
      "value": false,
      "factor": "symptoms_lt_48h",
      "points": 0.5,
      "present": true
    },
    {
      "factor": "rif_tenderness",
      "points": 0.0,
      "present": false
    },
    {
      "factor": "guarding",
      "points": 0.0,
      "present": false
    },
    {
      "factor": "rebound_tenderness",
      "points": 0.0,
      "present": false
    },
    {
      "factor": "rovsing_sign",
      "points": 0.0,
      "present": false
    },
    {
      "factor": "fever",
      "points": 0.0,
      "present": false
    },
    {
      "factor": "raised_wcc",
      "points": 0.0,
      "present": false
    },
    {
      "factor": "negative_urinalysis",
      "points": 0.0,
      "present": false
    },
    {
      "factor": "foreign_nric",
      "points": 0.0,
      "present": false
    }
  ],
  "age": 50,
  "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": "Chong CF, Adi MIW, Thien A, Suyoi A, Mackie AJ, Tin AS, Tripathi S, Jaman NH, Tan KK, Kok KY, Mathew VV, Paw O, Chua HB, Yapp SK",
    "id": "chong-2010",
    "pmid": "20428744",
    "source": "Singapore Med J. 2010;51(3):220-225",
    "title": "Development of the RIPASA score: a new appendicitis scoring system for the diagnosis of acute appendicitis"
  },
  "formula": "ripasa",
  "formula_expression": "RIPASA = (age<40 → 1.0; age≥40 → 0.5) + (male 1.0; female 0.5) + 0.5*rif_pain + 0.5*migration_to_rif + nausea_vomiting + anorexia + (symptoms_lt_48h 1.0; else 0.5) + rif_tenderness + 2*guarding + rebound_tenderness + 2*rovsing_sign + fever + raised_wcc + negative_urinalysis + foreign_nric; Chong 2010; max 16; <7.5 below_cutoff, ≥7.5 at_or_above_cutoff",
  "max_score": 16,
  "score": 1.5,
  "sex": "female",
  "ripasa_band": "below_cutoff"
}
```

## Errors

- HTTP 400 `invalid_ripasa_age`: age must be an integer from 1 to 120 (Chong 2010 RIPASA). Returned before settlement; you are not charged.
- 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

- [Alvarado score](https://magentlab.com/docs/alvarado) — Compute the Alvarado 1986 MANTRELS score from caller-assigned findings, temperature, WBC, and neutrophil percent.
- [AIR score](https://magentlab.com/docs/air) — Compute the Andersson 2008 appendicitis inflammatory response (AIR) score from caller-assigned findings, temperature, WBC, neutrophil percent, and CRP in mg/L.

## 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.
- 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.