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ASAS axial SpA classification criteria

ASAS axial SpA

Apply the 2009 ASAS classification criteria for axial spondyloarthritis (Rudwaleit set 3a / figure 2): require chronic back pain ≥3 months with age at onset <45, then return whether the imaging arm (sacroiliitis plus ≥1 SpA feature) or the clinical arm (HLA-B27 plus ≥2 other SpA features) classifies axial SpA. Not a diagnosis.

LIVE $0.005 USDC GET /api/calc/asas_axial_spa

Markdown: /docs/asas-axial-spa.md · Canonical: https://magentlab.com/docs/asas-axial-spa

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

What it computes

Apply the 2009 ASAS classification criteria for axial spondyloarthritis (Rudwaleit set 3a / figure 2): require chronic back pain ≥3 months with age at onset <45, then return whether the imaging arm (sacroiliitis plus ≥1 SpA feature) or the clinical arm (HLA-B27 plus ≥2 other SpA features) classifies axial SpA. Not a diagnosis.

When to use

When an agent already has caller-assigned Rudwaleit 2009 entry, imaging, and SpA feature flags and needs the published axial SpA classification result for research, not a diagnosis, not peripheral ASAS 2011, and not modified New York AS-only.

When not to use

• Not a medical device and not a diagnosis of axial spondyloarthritis or ankylosing spondylitis. Classification criteria for research.
• Entry (chronic_back_pain_ge_3_months true and age_at_onset_years 1–44) must be met or the request is HTTP 400 and is not returned as classified=false.
• MRI and radiographic sacroiliitis are caller-assigned. MRI means active (acute) inflammation highly suggestive of SpA-associated sacroiliitis. Radiographic means definite sacroiliitis according to modified New York (bilateral grade ≥2 or unilateral grade 3–4). magent does not read films.
• This tool is ASAS 2009 axial SpA classification (set 3a) only. It is not the 2011 peripheral ASAS criteria and not modified New York AS-only classification.
• HLA-B27 is obligatory in the clinical arm and does not count toward the two other SpA features. magent does not assay HLA-B27 or CRP.

Formula

ASAS 2009 axial SpA classification (Rudwaleit set 3a / fig 2 + table 5): required chronic_back_pain_ge_3_months true and age_at_onset_years 1–44 (age at onset <45). sacroiliitis_on_imaging = mri_sacroiliitis or radiographic_sacroiliitis. spa_feature_count = count of 11 SpA features (inflammatory_back_pain, arthritis, enthesitis_heel, uveitis, dactylitis, psoriasis, ibd, nsaid_good_response, family_history_spa, hla_b27, elevated_crp). other_spa_feature_count = spa_feature_count minus 1 if hla_b27 else spa_feature_count. imaging_arm iff sacroiliitis_on_imaging and spa_feature_count ≥1. clinical_arm iff hla_b27 and other_spa_feature_count ≥2. classified iff imaging_arm or clinical_arm. Not a diagnosis. Not peripheral ASAS 2011. Not modified New York AS-only

Citation

Title

The development of Assessment of SpondyloArthritis international Society classification criteria for axial spondyloarthritis (part II): validation and final selection

Authors

Rudwaleit M, van der Heijde D, Landewé R, Listing J, Akkoc N, Brandt J, Braun J, Chou CT, Collantes-Estevez E, Dougados M, Huang F, Gu J, Khan MA, Kirazli Y, Maksymowych WP, Mielants H, Sørensen IJ, Ozgocmen S, Roussou E, Valle-Oñate R, Weber U, Wei J, Sieper J

Source

Ann Rheum Dis. 2009;68(6):777-783

DOI

10.1136/ard.2009.108233

Worked example

Also searched as

• ASAS axial spondyloarthritis
• ASAS 2009 classification criteria
• Rudwaleit axial SpA
• axial spondyloarthritis classification
• HLA-B27 sacroiliitis criteria
• ASAS axSpA
• inflammatory back pain SpA classification
• not modified New York AS

Try

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

/api/calc/asas_axial_spa?chronic_back_pain_ge_3_months=true&age_at_onset_years=28&mri_sacroiliitis=true&radiographic_sacroiliitis=false&inflammatory_back_pain=true&arthritis=false&enthesitis_heel=false&uveitis=false&dactylitis=false&psoriasis=false&ibd=false&nsaid_good_response=false&family_history_spa=false&hla_b27=false&elevated_crp=false

Full URL: https://api.magentlab.com/api/calc/asas_axial_spa?chronic_back_pain_ge_3_months=true&age_at_onset_years=28&mri_sacroiliitis=true&radiographic_sacroiliitis=false&inflammatory_back_pain=true&arthritis=false&enthesitis_heel=false&uveitis=false&dactylitis=false&psoriasis=false&ibd=false&nsaid_good_response=false&family_history_spa=false&hla_b27=false&elevated_crp=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/asas_axial_spa?chronic_back_pain_ge_3_months=true&age_at_onset_years=28&mri_sacroiliitis=true&radiographic_sacroiliitis=false&inflammatory_back_pain=true&arthritis=false&enthesitis_heel=false&uveitis=false&dactylitis=false&psoriasis=false&ibd=false&nsaid_good_response=false&family_history_spa=false&hla_b27=false&elevated_crp=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/asas_axial_spa 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_at_onset_years": "28",
      "arthritis": "false",
      "chronic_back_pain_ge_3_months": "true",
      "dactylitis": "false",
      "elevated_crp": "false",
      "enthesitis_heel": "false",
      "family_history_spa": "false",
      "hla_b27": "false",
      "ibd": "false",
      "inflammatory_back_pain": "true",
      "mri_sacroiliitis": "true",
      "nsaid_good_response": "false",
      "psoriasis": "false",
      "radiographic_sacroiliitis": "false",
      "uveitis": "false"
    },
    {
      "age_at_onset_years": "28",
      "arthritis": "false",
      "chronic_back_pain_ge_3_months": "true",
      "dactylitis": "false",
      "elevated_crp": "false",
      "enthesitis_heel": "false",
      "family_history_spa": "false",
      "hla_b27": "false",
      "ibd": "false",
      "inflammatory_back_pain": "true",
      "mri_sacroiliitis": "true",
      "nsaid_good_response": "false",
      "psoriasis": "false",
      "radiographic_sacroiliitis": "false",
      "uveitis": "false"
    }
  ]
}

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/asas_axial_spa",
  "items": [
    {
      "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": "Rudwaleit M, van der Heijde D, Landewé R, Listing J, Akkoc N, Brandt J, Braun J, Chou CT, Collantes-Estevez E, Dougados M, Huang F, Gu J, Khan MA, Kirazli Y, Maksymowych WP, Mielants H, Sørensen IJ, Ozgocmen S, Roussou E, Valle-Oñate R, Weber U, Wei J, Sieper J",
        "doi": "10.1136/ard.2009.108233",
        "id": "rudwaleit-2009",
        "pmid": "19297345",
        "source": "Ann Rheum Dis. 2009;68(6):777-783",
        "title": "The development of Assessment of SpondyloArthritis international Society classification criteria for axial spondyloarthritis (part II): validation and final selection"
      },
      "formula": "asas_axial_spa",
      "formula_expression": "ASAS 2009 axial SpA classification (Rudwaleit set 3a / fig 2 + table 5): required chronic_back_pain_ge_3_months true and age_at_onset_years 1–44 (age at onset <45). sacroiliitis_on_imaging = mri_sacroiliitis or radiographic_sacroiliitis. spa_feature_count = count of 11 SpA features (inflammatory_back_pain, arthritis, enthesitis_heel, uveitis, dactylitis, psoriasis, ibd, nsaid_good_response, family_history_spa, hla_b27, elevated_crp). other_spa_feature_count = spa_feature_count minus 1 if hla_b27 else spa_feature_count. imaging_arm iff sacroiliitis_on_imaging and spa_feature_count ≥1. clinical_arm iff hla_b27 and other_spa_feature_count ≥2. classified iff imaging_arm or clinical_arm. Not a diagnosis. Not peripheral ASAS 2011. Not modified New York AS-only",
      "classified": true,
      "clinical_arm": false,
      "imaging_arm": true,
      "other_spa_feature_count": 1,
      "sacroiliitis_on_imaging": true,
      "spa_feature_count": 1
    },
    {
      "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": "Rudwaleit M, van der Heijde D, Landewé R, Listing J, Akkoc N, Brandt J, Braun J, Chou CT, Collantes-Estevez E, Dougados M, Huang F, Gu J, Khan MA, Kirazli Y, Maksymowych WP, Mielants H, Sørensen IJ, Ozgocmen S, Roussou E, Valle-Oñate R, Weber U, Wei J, Sieper J",
        "doi": "10.1136/ard.2009.108233",
        "id": "rudwaleit-2009",
        "pmid": "19297345",
        "source": "Ann Rheum Dis. 2009;68(6):777-783",
        "title": "The development of Assessment of SpondyloArthritis international Society classification criteria for axial spondyloarthritis (part II): validation and final selection"
      },
      "formula": "asas_axial_spa",
      "formula_expression": "ASAS 2009 axial SpA classification (Rudwaleit set 3a / fig 2 + table 5): required chronic_back_pain_ge_3_months true and age_at_onset_years 1–44 (age at onset <45). sacroiliitis_on_imaging = mri_sacroiliitis or radiographic_sacroiliitis. spa_feature_count = count of 11 SpA features (inflammatory_back_pain, arthritis, enthesitis_heel, uveitis, dactylitis, psoriasis, ibd, nsaid_good_response, family_history_spa, hla_b27, elevated_crp). other_spa_feature_count = spa_feature_count minus 1 if hla_b27 else spa_feature_count. imaging_arm iff sacroiliitis_on_imaging and spa_feature_count ≥1. clinical_arm iff hla_b27 and other_spa_feature_count ≥2. classified iff imaging_arm or clinical_arm. Not a diagnosis. Not peripheral ASAS 2011. Not modified New York AS-only",
      "classified": true,
      "clinical_arm": false,
      "imaging_arm": true,
      "other_spa_feature_count": 1,
      "sacroiliitis_on_imaging": true,
      "spa_feature_count": 1
    }
  ]
}

Response

Example JSON

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

{
  "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": "Rudwaleit M, van der Heijde D, Landewé R, Listing J, Akkoc N, Brandt J, Braun J, Chou CT, Collantes-Estevez E, Dougados M, Huang F, Gu J, Khan MA, Kirazli Y, Maksymowych WP, Mielants H, Sørensen IJ, Ozgocmen S, Roussou E, Valle-Oñate R, Weber U, Wei J, Sieper J",
    "doi": "10.1136/ard.2009.108233",
    "id": "rudwaleit-2009",
    "pmid": "19297345",
    "source": "Ann Rheum Dis. 2009;68(6):777-783",
    "title": "The development of Assessment of SpondyloArthritis international Society classification criteria for axial spondyloarthritis (part II): validation and final selection"
  },
  "formula": "asas_axial_spa",
  "formula_expression": "ASAS 2009 axial SpA classification (Rudwaleit set 3a / fig 2 + table 5): required chronic_back_pain_ge_3_months true and age_at_onset_years 1–44 (age at onset <45). sacroiliitis_on_imaging = mri_sacroiliitis or radiographic_sacroiliitis. spa_feature_count = count of 11 SpA features (inflammatory_back_pain, arthritis, enthesitis_heel, uveitis, dactylitis, psoriasis, ibd, nsaid_good_response, family_history_spa, hla_b27, elevated_crp). other_spa_feature_count = spa_feature_count minus 1 if hla_b27 else spa_feature_count. imaging_arm iff sacroiliitis_on_imaging and spa_feature_count ≥1. clinical_arm iff hla_b27 and other_spa_feature_count ≥2. classified iff imaging_arm or clinical_arm. Not a diagnosis. Not peripheral ASAS 2011. Not modified New York AS-only",
  "classified": true,
  "clinical_arm": false,
  "imaging_arm": true,
  "other_spa_feature_count": 1,
  "sacroiliitis_on_imaging": true,
  "spa_feature_count": 1
}

Client errors (HTTP 400)

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

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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.