CASPAR classification criteria

CASPAR

Apply the Taylor 2006 CASPAR classification criteria for psoriatic arthritis: require established inflammatory articular disease, then return the published point total (max 8) and whether score ≥3 classifies psoriatic arthritis. Not a diagnosis.

LIVE $0.005 USDC GET /api/calc/caspar

Markdown: /docs/caspar.md · Canonical: https://magentlab.com/docs/caspar

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

What it computes

When to use

When an agent already has caller-assigned Taylor 2006 entry and CASPAR items and needs the published classification result for research, not a diagnosis of psoriatic arthritis and not Moll and Wright criteria.

When not to use

Not a medical device and not a diagnosis of psoriatic arthritis. Classification criteria for research (Taylor 2006). Not Moll and Wright.
Entry (inflammatory_articular_disease true: established inflammatory articular disease of joint, spine, or enthesis) must be met or the request is HTTP 400 and is not returned as classified=false.
Current psoriasis scores 2 and excludes personal and family history points. Personal history scores 1 only when current psoriasis is false. Family history scores 1 only when current psoriasis and personal history are both false.
magent does not examine skin or nails, assay rheumatoid factor, or read films. Dactylitis is current swelling of an entire digit or a recorded history. Juxtaarticular new bone excludes osteophyte formation.

Formula

Taylor 2006 CASPAR: required inflammatory_articular_disease true (established inflammatory articular disease of joint, spine, or enthesis; else do not score). Score = current_psoriasis 2 + personal_history_psoriasis 1 (only if current_psoriasis false) + family_history_psoriasis 1 (only if current_psoriasis false and personal_history_psoriasis false) + nail_dystrophy 1 + rheumatoid_factor_negative 1 + dactylitis 1 + juxtaarticular_new_bone 1; max 8; classified iff score ≥3. Not a diagnosis. Not Moll and Wright

Citation

Title: Classification criteria for psoriatic arthritis: development of new criteria from a large international study
Authors: Taylor W, Gladman D, Helliwell P, Marchesoni A, Mease P, Mielants H, CASPAR Study Group
Source: Arthritis Rheum. 2006;54(8):2665-2673
DOI: 10.1002/art.21972

Worked example

Current psoriasis, RF-negative, and dactylitis, classified

Given: current_psoriasis=truedactylitis=truefamily_history_psoriasis=falseinflammatory_articular_disease=truejuxtaarticular_new_bone=falsenail_dystrophy=falsepersonal_history_psoriasis=falserheumatoid_factor_negative=true

Required: inflammatory_articular_disease true
current_psoriasis 2; personal and family history do not add
rheumatoid_factor_negative 1 + dactylitis 1
score = 4 (max 8) ≥3; classified true; band classified

Personal history path, classified

Given: current_psoriasis=falsedactylitis=falsefamily_history_psoriasis=trueinflammatory_articular_disease=truejuxtaarticular_new_bone=falsenail_dystrophy=truepersonal_history_psoriasis=truerheumatoid_factor_negative=true

current_psoriasis false; personal_history_psoriasis 1
family_history_psoriasis true does not add because personal history is true
nail_dystrophy 1 + rheumatoid_factor_negative 1
score = 3 (max 8) ≥3; classified true; band classified

Entry met, current psoriasis only, not classified

Given: current_psoriasis=truedactylitis=falsefamily_history_psoriasis=falseinflammatory_articular_disease=truejuxtaarticular_new_bone=falsenail_dystrophy=falsepersonal_history_psoriasis=falserheumatoid_factor_negative=false

current_psoriasis 2; remaining scoring flags false
score = 2 (max 8) <3; classified false; band not_classified

Nail dystrophy, RF-negative, and dactylitis, classified

Given: current_psoriasis=falsedactylitis=truefamily_history_psoriasis=falseinflammatory_articular_disease=truejuxtaarticular_new_bone=falsenail_dystrophy=truepersonal_history_psoriasis=falserheumatoid_factor_negative=true

No psoriasis items; nail_dystrophy 1 + rheumatoid_factor_negative 1 + dactylitis 1
score = 3 (max 8) ≥3; classified true; band classified

Family history plus juxtaarticular new bone, classified

Given: current_psoriasis=falsedactylitis=falsefamily_history_psoriasis=trueinflammatory_articular_disease=truejuxtaarticular_new_bone=truenail_dystrophy=falsepersonal_history_psoriasis=falserheumatoid_factor_negative=true

current and personal history false; family_history_psoriasis 1
juxtaarticular_new_bone 1 + rheumatoid_factor_negative 1
score = 3 (max 8) ≥3; classified true; band classified

Also searched as

CASPAR criteria
Taylor 2006 CASPAR
psoriatic arthritis classification
CASPAR Study Group
not Moll and Wright
psoriatic nail dystrophy classification
juxtaarticular new bone formation
CASPAR psoriatic arthritis

Try

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

/api/calc/caspar?inflammatory_articular_disease=true&current_psoriasis=true&personal_history_psoriasis=false&family_history_psoriasis=false&nail_dystrophy=false&rheumatoid_factor_negative=true&dactylitis=true&juxtaarticular_new_bone=false

Full URL: https://api.magentlab.com/api/calc/caspar?inflammatory_articular_disease=true&current_psoriasis=true&personal_history_psoriasis=false&family_history_psoriasis=false&nail_dystrophy=false&rheumatoid_factor_negative=true&dactylitis=true&juxtaarticular_new_bone=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/caspar?inflammatory_articular_disease=true&current_psoriasis=true&personal_history_psoriasis=false&family_history_psoriasis=false&nail_dystrophy=false&rheumatoid_factor_negative=true&dactylitis=true&juxtaarticular_new_bone=false"

Parameters

Name	Type	Required	Description
`inflammatory_articular_disease`	boolean	required	Must be true. Taylor 2006 CASPAR entry: established inflammatory articular disease of joint, spine, or enthesis as assigned by the caller. false is invalid and is not classified=false. magent does not examine joints.
`current_psoriasis`	boolean	required	Current psoriasis as assigned by the caller (Taylor 2006): psoriatic skin or scalp disease present today as judged by a rheumatologist or dermatologist. true scores 2. When true, personal_history_psoriasis and family_history_psoriasis do not add. magent does not examine skin.
`personal_history_psoriasis`	boolean	required	Personal history of psoriasis as assigned by the caller (Taylor 2006): a history that may be obtained from the patient, family physician, dermatologist, rheumatologist, or other qualified health care provider. true scores 1 only if current_psoriasis is false. magent does not examine skin.
`family_history_psoriasis`	boolean	required	Family history of psoriasis as assigned by the caller (Taylor 2006): first- or second-degree relative according to patient report. true scores 1 only if current_psoriasis is false and personal_history_psoriasis is false. magent does not take a pedigree.
`nail_dystrophy`	boolean	required	Typical psoriatic nail dystrophy including onycholysis, pitting, and hyperkeratosis on current examination, as assigned by the caller (Taylor 2006). true scores 1. magent does not examine nails.
`rheumatoid_factor_negative`	boolean	required	Negative rheumatoid factor by any method except latex, preferably ELISA or nephelometry according to the local laboratory reference range, as assigned by the caller (Taylor 2006). true scores 1. magent does not assay rheumatoid factor.
`dactylitis`	boolean	required	Current swelling of an entire digit, or a history of dactylitis recorded by a rheumatologist, as assigned by the caller (Taylor 2006). true scores 1. magent does not examine digits.
`juxtaarticular_new_bone`	boolean	required	Radiographic ill-defined ossification near joint margins, excluding osteophyte formation, on plain radiographs of the hand or foot, as assigned by the caller (Taylor 2006). true scores 1. magent does not read films.

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/caspar 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": [
    {
      "current_psoriasis": "true",
      "dactylitis": "true",
      "family_history_psoriasis": "false",
      "inflammatory_articular_disease": "true",
      "juxtaarticular_new_bone": "false",
      "nail_dystrophy": "false",
      "personal_history_psoriasis": "false",
      "rheumatoid_factor_negative": "true"
    },
    {
      "current_psoriasis": "true",
      "dactylitis": "true",
      "family_history_psoriasis": "false",
      "inflammatory_articular_disease": "true",
      "juxtaarticular_new_bone": "false",
      "nail_dystrophy": "false",
      "personal_history_psoriasis": "false",
      "rheumatoid_factor_negative": "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/caspar",
  "items": [
    {
      "band": "classified",
      "components": [
        {
          "factor": "current_psoriasis",
          "points": 2,
          "present": true
        },
        {
          "factor": "personal_history_psoriasis",
          "points": 0,
          "present": false
        },
        {
          "factor": "family_history_psoriasis",
          "points": 0,
          "present": false
        },
        {
          "factor": "nail_dystrophy",
          "points": 0,
          "present": false
        },
        {
          "factor": "rheumatoid_factor_negative",
          "points": 1,
          "present": true
        },
        {
          "factor": "dactylitis",
          "points": 1,
          "present": true
        },
        {
          "factor": "juxtaarticular_new_bone",
          "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": "Taylor W, Gladman D, Helliwell P, Marchesoni A, Mease P, Mielants H, CASPAR Study Group",
        "doi": "10.1002/art.21972",
        "id": "taylor-2006",
        "pmid": "16871531",
        "source": "Arthritis Rheum. 2006;54(8):2665-2673",
        "title": "Classification criteria for psoriatic arthritis: development of new criteria from a large international study"
      },
      "formula": "caspar",
      "formula_expression": "Taylor 2006 CASPAR: required inflammatory_articular_disease true (established inflammatory articular disease of joint, spine, or enthesis; else do not score). Score = current_psoriasis 2 + personal_history_psoriasis 1 (only if current_psoriasis false) + family_history_psoriasis 1 (only if current_psoriasis false and personal_history_psoriasis false) + nail_dystrophy 1 + rheumatoid_factor_negative 1 + dactylitis 1 + juxtaarticular_new_bone 1; max 8; classified iff score ≥3. Not a diagnosis. Not Moll and Wright",
      "max_score": 8,
      "score": 4,
      "classified": true
    },
    {
      "band": "classified",
      "components": [
        {
          "factor": "current_psoriasis",
          "points": 2,
          "present": true
        },
        {
          "factor": "personal_history_psoriasis",
          "points": 0,
          "present": false
        },
        {
          "factor": "family_history_psoriasis",
          "points": 0,
          "present": false
        },
        {
          "factor": "nail_dystrophy",
          "points": 0,
          "present": false
        },
        {
          "factor": "rheumatoid_factor_negative",
          "points": 1,
          "present": true
        },
        {
          "factor": "dactylitis",
          "points": 1,
          "present": true
        },
        {
          "factor": "juxtaarticular_new_bone",
          "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": "Taylor W, Gladman D, Helliwell P, Marchesoni A, Mease P, Mielants H, CASPAR Study Group",
        "doi": "10.1002/art.21972",
        "id": "taylor-2006",
        "pmid": "16871531",
        "source": "Arthritis Rheum. 2006;54(8):2665-2673",
        "title": "Classification criteria for psoriatic arthritis: development of new criteria from a large international study"
      },
      "formula": "caspar",
      "formula_expression": "Taylor 2006 CASPAR: required inflammatory_articular_disease true (established inflammatory articular disease of joint, spine, or enthesis; else do not score). Score = current_psoriasis 2 + personal_history_psoriasis 1 (only if current_psoriasis false) + family_history_psoriasis 1 (only if current_psoriasis false and personal_history_psoriasis false) + nail_dystrophy 1 + rheumatoid_factor_negative 1 + dactylitis 1 + juxtaarticular_new_bone 1; max 8; classified iff score ≥3. Not a diagnosis. Not Moll and Wright",
      "max_score": 8,
      "score": 4,
      "classified": true
    }
  ]
}

Response

Field	Type	Description
`formula`	string	caspar
`formula_expression`	string	Taylor 2006 CASPAR classification expression
`score`	integer	Taylor 2006 CASPAR points. Integer 0–8.
`max_score`	integer	8
`classified`	boolean	true iff score ≥3. Classification criteria for research, not a diagnosis of psoriatic arthritis. Not Moll and Wright.
`band`	string	classified when score ≥3; not_classified otherwise. Not a diagnosis. Not Moll and Wright.
`components`	array	Per-item Taylor 2006 CASPAR points
`citation`	object	Taylor 2006 Arthritis Rheum citation
`disclaimer`	string	Not-a-device notice

Example JSON

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

{
  "band": "classified",
  "components": [
    {
      "factor": "current_psoriasis",
      "points": 2,
      "present": true
    },
    {
      "factor": "personal_history_psoriasis",
      "points": 0,
      "present": false
    },
    {
      "factor": "family_history_psoriasis",
      "points": 0,
      "present": false
    },
    {
      "factor": "nail_dystrophy",
      "points": 0,
      "present": false
    },
    {
      "factor": "rheumatoid_factor_negative",
      "points": 1,
      "present": true
    },
    {
      "factor": "dactylitis",
      "points": 1,
      "present": true
    },
    {
      "factor": "juxtaarticular_new_bone",
      "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": "Taylor W, Gladman D, Helliwell P, Marchesoni A, Mease P, Mielants H, CASPAR Study Group",
    "doi": "10.1002/art.21972",
    "id": "taylor-2006",
    "pmid": "16871531",
    "source": "Arthritis Rheum. 2006;54(8):2665-2673",
    "title": "Classification criteria for psoriatic arthritis: development of new criteria from a large international study"
  },
  "formula": "caspar",
  "formula_expression": "Taylor 2006 CASPAR: required inflammatory_articular_disease true (established inflammatory articular disease of joint, spine, or enthesis; else do not score). Score = current_psoriasis 2 + personal_history_psoriasis 1 (only if current_psoriasis false) + family_history_psoriasis 1 (only if current_psoriasis false and personal_history_psoriasis false) + nail_dystrophy 1 + rheumatoid_factor_negative 1 + dactylitis 1 + juxtaarticular_new_bone 1; max 8; classified iff score ≥3. Not a diagnosis. Not Moll and Wright",
  "max_score": 8,
  "score": 4,
  "classified": true
}

Client errors (HTTP 400)

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

HTTP	Code	When
400	`invalid_caspar`	inflammatory_articular_disease must be true (Taylor 2006 CASPAR entry: established inflammatory articular disease of joint, spine, or enthesis). Returned before settlement; you are not charged.
400	`invalid_flag`	boolean clinical flags must be true or false Returned before settlement; you are not charged.
400	`invalid_items`	POST body must be a JSON object with only an items array Returned before settlement; you are not charged.
400	`invalid_item_count`	items must be an array of 1 to 25 objects Returned before settlement; you are not charged.
400	`invalid_item`	each items entry must be a JSON object Returned before settlement; you are not charged.

Related tools

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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.