Emergency · LIVE

Leiden undifferentiated arthritis prediction rule

Leiden UA rule

Sum the van der Helm-van Mil 2007 simplified Leiden prediction score for recent-onset undifferentiated arthritis and return the paper’s ≤6 / 6–8 / ≥8 decision band.

LIVE $0.005 USDC GET /api/calc/leiden_arthritis

Markdown: /docs/leiden-arthritis.md · Canonical: https://magentlab.com/docs/leiden-arthritis

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

What it computes

Sum the van der Helm-van Mil 2007 simplified Leiden prediction score for recent-onset undifferentiated arthritis and return the paper’s ≤6 / 6–8 / ≥8 decision band.

When to use

When an agent already has age, sex, caller-assigned joint-distribution flags, 100-mm morning-stiffness VAS, tender and swollen joint counts, CRP in mg/L, and RF/anti-CCP flags and needs the published Leiden UA score, not an RA diagnosis.

When not to use

• Not a medical device and not a diagnosis of rheumatoid arthritis or a treatment order.
• magent does not examine joints or assay serologies. Age, sex, distribution flags, 100-mm VAS, joint counts, CRP, RF, and anti-CCP are caller-assigned.
• Morning stiffness is the published 100-mm VAS severity, not duration in minutes.
• If upper_and_lower_extremities is true, the 1-point upper_extremities row is ignored (1.5 only). Small-joint and symmetric rows may stack with that extremity row.
• The total is rounded to the nearest number ending in .0 or .5 (paper Table 3). Bands are the paper decision cutoffs: ≤6 low, >6 and <8 indeterminate, ≥8 high. max_score 14. Not a classification of RA.

Formula

Leiden UA score (van der Helm-van Mil 2007 Figure 1 / Table 2) = age_years*0.02 + female 1 + small_joints_hands_feet 0.5 + symmetric 0.5 + (upper_and_lower_extremities 1.5 else upper_extremities 1) + morning_stiffness_vas_mm (0–25 → 0; 26–90 → 1; >90 → 2) + tender_joint_count (<4 → 0; 4–10 → 0.5; ≥11 → 1) + swollen_joint_count (<4 → 0; 4–10 → 0.5; ≥11 → 1) + crp_mg_l (0–4 → 0; 5–50 → 0.5; ≥51 → 1.5) + rheumatoid_factor_positive 1 + anti_ccp_positive 2; round to nearest 0.0 or 0.5; ≤6 low, >6 and <8 indeterminate, ≥8 high; max 14; not a diagnosis of RA

Citation

Title

A prediction rule for disease outcome in patients with recent-onset undifferentiated arthritis: how to guide individual treatment decisions

Authors

van der Helm-van Mil AH, le Cessie S, van Dongen H, Breedveld FC, Toes RE, Huizinga TW

Source

Arthritis Rheum. 2007;56(2):433-440

DOI

10.1002/art.22380

Worked example

Also searched as

• Leiden prediction rule
• Leiden UA rule
• undifferentiated arthritis score
• van der Helm-van Mil 2007
• early arthritis prediction rule
• Leiden RA prediction score

Try

Opens the live endpoint. Unpaid browser requests show the paywall; agents should send Accept: application/json.

/api/calc/leiden_arthritis?age=48&sex=female&small_joints_hands_feet=true&symmetric=true&upper_extremities=true&upper_and_lower_extremities=false&morning_stiffness_vas_mm=50&tender_joint_count=8&swollen_joint_count=8&crp_mg_l=60&rheumatoid_factor_positive=false&anti_ccp_positive=false

Full URL: https://api.magentlab.com/api/calc/leiden_arthritis?age=48&sex=female&small_joints_hands_feet=true&symmetric=true&upper_extremities=true&upper_and_lower_extremities=false&morning_stiffness_vas_mm=50&tender_joint_count=8&swollen_joint_count=8&crp_mg_l=60&rheumatoid_factor_positive=false&anti_ccp_positive=false

Call

Expect HTTP 402 until you retry with PAYMENT-SIGNATURE. Incomplete query params return HTTP 400 before any quote or charge.

curl -i -H "Accept: application/json" "https://api.magentlab.com/api/calc/leiden_arthritis?age=48&sex=female&small_joints_hands_feet=true&symmetric=true&upper_extremities=true&upper_and_lower_extremities=false&morning_stiffness_vas_mm=50&tender_joint_count=8&swollen_joint_count=8&crp_mg_l=60&rheumatoid_factor_positive=false&anti_ccp_positive=false"

Parameters

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.

POST /api/calc/leiden_arthritis Max 25 unit_amount + extra_item_amount * (n - 1) extra $0.002 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 (fixture)

{
  "items": [
    {
      "age": "48",
      "anti_ccp_positive": "false",
      "crp_mg_l": "60",
      "morning_stiffness_vas_mm": "50",
      "rheumatoid_factor_positive": "false",
      "sex": "female",
      "small_joints_hands_feet": "true",
      "swollen_joint_count": "8",
      "symmetric": "true",
      "tender_joint_count": "8",
      "upper_and_lower_extremities": "false",
      "upper_extremities": "true"
    },
    {
      "age": "48",
      "anti_ccp_positive": "false",
      "crp_mg_l": "60",
      "morning_stiffness_vas_mm": "50",
      "rheumatoid_factor_positive": "false",
      "sex": "female",
      "small_joints_hands_feet": "true",
      "swollen_joint_count": "8",
      "symmetric": "true",
      "tender_joint_count": "8",
      "upper_and_lower_extremities": "false",
      "upper_extremities": "true"
    }
  ]
}

Open bulk paywall →

Opens a two-item fixture on the API host. Unpaid browsers get the same MetaMask paywall as GET; Pay retries POST with those items.

Example 200 (fixture)

{
  "count": 2,
  "path": "/api/calc/leiden_arthritis",
  "items": [
    {
      "components": [
        {
          "value": 48,
          "factor": "age",
          "points": 0.96,
          "present": true
        },
        {
          "value": "female",
          "factor": "female",
          "points": 1,
          "present": true
        },
        {
          "factor": "small_joints_hands_feet",
          "points": 0.5,
          "present": true
        },
        {
          "factor": "symmetric",
          "points": 0.5,
          "present": true
        },
        {
          "factor": "upper_and_lower_extremities",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "upper_extremities",
          "points": 1.0,
          "present": true
        },
        {
          "value": 50.0,
          "factor": "morning_stiffness_vas_mm",
          "points": 1,
          "present": true
        },
        {
          "value": 8,
          "factor": "tender_joint_count",
          "points": 0.5,
          "present": true
        },
        {
          "value": 8,
          "factor": "swollen_joint_count",
          "points": 0.5,
          "present": true
        },
        {
          "value": 60.0,
          "factor": "crp_mg_l",
          "points": 1.5,
          "present": true
        },
        {
          "factor": "rheumatoid_factor_positive",
          "points": 0,
          "present": false
        },
        {
          "factor": "anti_ccp_positive",
          "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": "van der Helm-van Mil AH, le Cessie S, van Dongen H, Breedveld FC, Toes RE, Huizinga TW",
        "doi": "10.1002/art.22380",
        "id": "van-der-helm-van-mil-2007",
        "pmid": "17265478",
        "source": "Arthritis Rheum. 2007;56(2):433-440",
        "title": "A prediction rule for disease outcome in patients with recent-onset undifferentiated arthritis: how to guide individual treatment decisions"
      },
      "formula": "leiden_arthritis",
      "formula_expression": "Leiden UA score (van der Helm-van Mil 2007 Figure 1 / Table 2) = age_years*0.02 + female 1 + small_joints_hands_feet 0.5 + symmetric 0.5 + (upper_and_lower_extremities 1.5 else upper_extremities 1) + morning_stiffness_vas_mm (0–25 → 0; 26–90 → 1; >90 → 2) + tender_joint_count (<4 → 0; 4–10 → 0.5; ≥11 → 1) + swollen_joint_count (<4 → 0; 4–10 → 0.5; ≥11 → 1) + crp_mg_l (0–4 → 0; 5–50 → 0.5; ≥51 → 1.5) + rheumatoid_factor_positive 1 + anti_ccp_positive 2; round to nearest 0.0 or 0.5; ≤6 low, >6 and <8 indeterminate, ≥8 high; max 14; not a diagnosis of RA",
      "max_score": 14,
      "score": 7.5,
      "leiden_band": "indeterminate"
    },
    {
      "components": [
        {
          "value": 48,
          "factor": "age",
          "points": 0.96,
          "present": true
        },
        {
          "value": "female",
          "factor": "female",
          "points": 1,
          "present": true
        },
        {
          "factor": "small_joints_hands_feet",
          "points": 0.5,
          "present": true
        },
        {
          "factor": "symmetric",
          "points": 0.5,
          "present": true
        },
        {
          "factor": "upper_and_lower_extremities",
          "points": 0.0,
          "present": false
        },
        {
          "factor": "upper_extremities",
          "points": 1.0,
          "present": true
        },
        {
          "value": 50.0,
          "factor": "morning_stiffness_vas_mm",
          "points": 1,
          "present": true
        },
        {
          "value": 8,
          "factor": "tender_joint_count",
          "points": 0.5,
          "present": true
        },
        {
          "value": 8,
          "factor": "swollen_joint_count",
          "points": 0.5,
          "present": true
        },
        {
          "value": 60.0,
          "factor": "crp_mg_l",
          "points": 1.5,
          "present": true
        },
        {
          "factor": "rheumatoid_factor_positive",
          "points": 0,
          "present": false
        },
        {
          "factor": "anti_ccp_positive",
          "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": "van der Helm-van Mil AH, le Cessie S, van Dongen H, Breedveld FC, Toes RE, Huizinga TW",
        "doi": "10.1002/art.22380",
        "id": "van-der-helm-van-mil-2007",
        "pmid": "17265478",
        "source": "Arthritis Rheum. 2007;56(2):433-440",
        "title": "A prediction rule for disease outcome in patients with recent-onset undifferentiated arthritis: how to guide individual treatment decisions"
      },
      "formula": "leiden_arthritis",
      "formula_expression": "Leiden UA score (van der Helm-van Mil 2007 Figure 1 / Table 2) = age_years*0.02 + female 1 + small_joints_hands_feet 0.5 + symmetric 0.5 + (upper_and_lower_extremities 1.5 else upper_extremities 1) + morning_stiffness_vas_mm (0–25 → 0; 26–90 → 1; >90 → 2) + tender_joint_count (<4 → 0; 4–10 → 0.5; ≥11 → 1) + swollen_joint_count (<4 → 0; 4–10 → 0.5; ≥11 → 1) + crp_mg_l (0–4 → 0; 5–50 → 0.5; ≥51 → 1.5) + rheumatoid_factor_positive 1 + anti_ccp_positive 2; round to nearest 0.0 or 0.5; ≤6 low, >6 and <8 indeterminate, ≥8 high; max 14; not a diagnosis of RA",
      "max_score": 14,
      "score": 7.5,
      "leiden_band": "indeterminate"
    }
  ]
}

Response

Example JSON

Machine form of the same example. Frozen fixture. Not a live lookup.

{
  "components": [
    {
      "value": 48,
      "factor": "age",
      "points": 0.96,
      "present": true
    },
    {
      "value": "female",
      "factor": "female",
      "points": 1,
      "present": true
    },
    {
      "factor": "small_joints_hands_feet",
      "points": 0.5,
      "present": true
    },
    {
      "factor": "symmetric",
      "points": 0.5,
      "present": true
    },
    {
      "factor": "upper_and_lower_extremities",
      "points": 0.0,
      "present": false
    },
    {
      "factor": "upper_extremities",
      "points": 1.0,
      "present": true
    },
    {
      "value": 50.0,
      "factor": "morning_stiffness_vas_mm",
      "points": 1,
      "present": true
    },
    {
      "value": 8,
      "factor": "tender_joint_count",
      "points": 0.5,
      "present": true
    },
    {
      "value": 8,
      "factor": "swollen_joint_count",
      "points": 0.5,
      "present": true
    },
    {
      "value": 60.0,
      "factor": "crp_mg_l",
      "points": 1.5,
      "present": true
    },
    {
      "factor": "rheumatoid_factor_positive",
      "points": 0,
      "present": false
    },
    {
      "factor": "anti_ccp_positive",
      "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": "van der Helm-van Mil AH, le Cessie S, van Dongen H, Breedveld FC, Toes RE, Huizinga TW",
    "doi": "10.1002/art.22380",
    "id": "van-der-helm-van-mil-2007",
    "pmid": "17265478",
    "source": "Arthritis Rheum. 2007;56(2):433-440",
    "title": "A prediction rule for disease outcome in patients with recent-onset undifferentiated arthritis: how to guide individual treatment decisions"
  },
  "formula": "leiden_arthritis",
  "formula_expression": "Leiden UA score (van der Helm-van Mil 2007 Figure 1 / Table 2) = age_years*0.02 + female 1 + small_joints_hands_feet 0.5 + symmetric 0.5 + (upper_and_lower_extremities 1.5 else upper_extremities 1) + morning_stiffness_vas_mm (0–25 → 0; 26–90 → 1; >90 → 2) + tender_joint_count (<4 → 0; 4–10 → 0.5; ≥11 → 1) + swollen_joint_count (<4 → 0; 4–10 → 0.5; ≥11 → 1) + crp_mg_l (0–4 → 0; 5–50 → 0.5; ≥51 → 1.5) + rheumatoid_factor_positive 1 + anti_ccp_positive 2; round to nearest 0.0 or 0.5; ≤6 low, >6 and <8 indeterminate, ≥8 high; max 14; not a diagnosis of RA",
  "max_score": 14,
  "score": 7.5,
  "leiden_band": "indeterminate"
}

Client errors (HTTP 400)

Invalid params return 400 without charge. Shared HTTP 402 and 503 meanings: Payments.

Related tools

• ACR/EULAR gout — Apply the 2015 ACR/EULAR gout classification criteria (Neogi Table 2): require the entry episode, classify immediately if MSU crystals are present, otherwise return the Step 3 score (max 23) and whether score ≥8 classifies gout. Not a gout diagnosis.
• SDAI — Sum caller-assigned 28-joint swollen and tender counts, 0–10 cm patient and evaluator globals, and CRP in mg/dL, and return the Aletaha 2005 SDAI with the newly proposed activity state.
• ACR/EULAR PMR — Apply the 2012 EULAR/ACR polymyalgia rheumatica classification criteria (Dasgupta Table 4): require age ≥50, bilateral shoulder aching, and abnormal CRP and/or ESR, then return the clinical score with or without optional ultrasound and whether the published cut point classifies PMR. Not a PMR diagnosis.

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. Unpaid valid requests return HTTP 402 with a base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote: retry the same PAYMENT-SIGNATURE. Full handshake and shared payment errors: Payments. Stdio MCP: /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.