{"uid":"cap_BnRALc1qWxqgn4AHMoPAm","slug":"asas-2009-axial-spondyloarthritis-classification-calculator-702d2cd5","name":"ASAS 2009 Axial Spondyloarthritis Classification Calculator","description":"ASAS 2009 axial SpA classification (Rudwaleit set 3a / fig 2). Required: chronic back pain ≥3 months and age at onset <45. Imaging arm: MRI or modified New York sacroiliitis plus ≥1 of 11 SpA features. Clinical arm: HLA-B27 plus ≥2 other features (HLA-B27 does not count toward those two). Not a diagnosis. Not peripheral ASAS 2011. Not modified New York AS-only. magent does not read films or assay HLA-B27.","url":"https://api.magentlab.com/api/calc/asas_axial_spa","method":"GET","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method"],"properties":{"type":{"type":"string","const":"http"},"method":{"enum":["GET","HEAD","DELETE"],"type":"string"},"headers":{"type":"object","additionalProperties":{"type":"string"}},"queryParams":{"type":"object","required":["chronic_back_pain_ge_3_months","age_at_onset_years","mri_sacroiliitis","radiographic_sacroiliitis","inflammatory_back_pain","arthritis","enthesitis_heel","uveitis","dactylitis","psoriasis","ibd","nsaid_good_response","family_history_spa","hla_b27","elevated_crp"],"properties":{"ibd":{"type":"boolean","description":"Past or present Crohn's disease or ulcerative colitis diagnosed by a physician, as assigned by the caller (Rudwaleit 2009). true or false. magent does not diagnose IBD."},"hla_b27":{"type":"boolean","description":"HLA-B27 positive as assigned by the caller (Rudwaleit 2009). Obligatory for the clinical arm; does not count toward the two other SpA features. Counts toward spa_feature_count and the imaging arm. true or false. magent does not assay HLA-B27."},"uveitis":{"type":"boolean","description":"Past or present uveitis confirmed by an ophthalmologist, as assigned by the caller (Rudwaleit 2009). true or false. magent does not examine the eye."},"arthritis":{"type":"boolean","description":"Past or present synovitis diagnosed by a physician, as assigned by the caller (Rudwaleit 2009). true or false. magent does not examine joints."},"psoriasis":{"type":"boolean","description":"Past or present psoriasis diagnosed by a physician, as assigned by the caller (Rudwaleit 2009). true or false. magent does not examine skin."},"dactylitis":{"type":"boolean","description":"Past or present dactylitis diagnosed by a physician, as assigned by the caller (Rudwaleit 2009). true or false. magent does not examine digits."},"elevated_crp":{"type":"boolean","description":"CRP above the upper limit of normal in the presence of back pain after exclusion of other causes, as assigned by the caller (Rudwaleit 2009). true or false. magent does not assay CRP."},"enthesitis_heel":{"type":"boolean","description":"Past or present spontaneous pain or tenderness at the insertion of the Achilles tendon or plantar fascia at the calcaneus, as assigned by the caller (Rudwaleit 2009). Heel enthesitis only. true or false. magent does not examine entheses."},"mri_sacroiliitis":{"type":"boolean","description":"Active (acute) inflammation on MRI highly suggestive of SpA-associated sacroiliitis, as assigned by the caller (Rudwaleit 2009). Combined with radiographic_sacroiliitis by OR for sacroiliitis_on_imaging. true or false. magent does not read MRI."},"age_at_onset_years":{"type":"integer","description":"Age at onset of back pain in years, integer 1–44 (Rudwaleit 2009 entry: age at onset <45). 0 and ≥45 are invalid and are not classified. magent does not date the patient."},"family_history_spa":{"type":"boolean","description":"Family history of SpA as assigned by the caller (Rudwaleit 2009): first-degree or second-degree relatives with ankylosing spondylitis, psoriasis, acute uveitis, reactive arthritis, or IBD. true or false. magent does not take a pedigree."},"nsaid_good_response":{"type":"boolean","description":"Good response to NSAIDs as assigned by the caller (Rudwaleit 2009): 24–48 h after a full dose of NSAID the back pain is not present anymore or is much better. true or false. magent does not prescribe NSAIDs."},"inflammatory_back_pain":{"type":"boolean","description":"Inflammatory back pain as assigned by the caller (Rudwaleit 2009 fig 2 / table 5). true or false. magent does not take a history or apply a nested IBP questionnaire."},"radiographic_sacroiliitis":{"type":"boolean","description":"Definite radiographic sacroiliitis according to modified New York criteria (bilateral grade ≥2 or unilateral grade 3–4), as assigned by the caller (Rudwaleit 2009). true or false. magent does not read radiographs."},"chronic_back_pain_ge_3_months":{"type":"boolean","description":"Must be true. Rudwaleit 2009 entry: chronic back pain ≥3 months. false is invalid and is not returned as classified=false. magent does not take a history."}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object"}}}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.005","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.005/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_StvtzofXktiu_JF2voihi","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.005","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Applies the ASAS 2009 axial spondyloarthritis classification criteria (Rudwaleit set 3a) via imaging and clinical arms to determine if a patient meets criteria for axial SpA classification.","exampleAgentPrompt":"My patient has had chronic back pain for over 3 months with onset at age 32. MRI shows sacroiliitis, and they also have a positive HLA-B27, inflammatory back pain, and a history of uveitis. Can you run the ASAS 2009 axial SpA classification — no radiographic sacroiliitis, no arthritis, no enthesitis, no dactylitis, no psoriasis, no IBD, good NSAID response, no family history, and elevated CRP?","exampleUseCases":[{"title":"Rheumatology clinic documentation support","prompt":"I need to classify a 28-year-old patient with chronic back pain starting at age 24. MRI shows sacroiliitis. They have inflammatory back pain and dactylitis, are HLA-B27 positive, have elevated CRP, no radiographic sacroiliitis, no arthritis, no enthesitis, no uveitis, no psoriasis, no IBD, no NSAID response, and no family history. Run the ASAS 2009 axial SpA classification for me."},{"title":"HLA-B27 positive patient with no imaging findings","prompt":"Can you check ASAS 2009 axial SpA criteria for a patient with chronic back pain onset at age 38, HLA-B27 positive, no MRI or radiographic sacroiliitis, but with inflammatory back pain and a good response to NSAIDs? No arthritis, enthesitis, uveitis, dactylitis, psoriasis, IBD, family history, or elevated CRP."},{"title":"Research cohort eligibility screening","prompt":"For a research cohort, I need to check ASAS 2009 axial SpA classification for a 41-year-old with back pain since age 36. Radiographic sacroiliitis is present, HLA-B27 negative, inflammatory back pain yes, family history of SpA yes, uveitis yes, no arthritis, no enthesitis, no dactylitis, no psoriasis, no IBD, no NSAID response, elevated CRP false. Does this patient meet classification criteria?"}],"resultDescription":"Returns a structured result indicating whether the patient meets ASAS 2009 axial SpA classification criteria, specifying which arm (imaging or clinical) was satisfied, the count of SpA features present, and the logical breakdown of each arm's criteria evaluation. This is a classification tool, not a clinical diagnosis.","failureModes":["Missing required boolean parameters (e.g. chronic_back_pain_ge_3_months, hla_b27) returns a validation error","Age at onset ≥45 or chronic back pain <3 months causes entry criteria failure — patient is not classifiable","HLA-B27 false with no imaging findings means neither arm can be satisfied","Caller misassigning clinical findings (e.g. counting HLA-B27 as one of the two required clinical arm SpA features) will yield incorrect results — the API enforces that HLA-B27 is obligatory but does not count toward the two other features","Peripheral ASAS 2011 criteria or modified New York AS-only criteria cannot be applied by this endpoint"],"whenToPreferThis":"Use this endpoint when you need to apply specifically the ASAS 2009 axial SpA classification criteria (Rudwaleit, set 3a / fig 2) — covering both the imaging arm and the clinical HLA-B27 arm — for patients with chronic back pain of ≥3 months and onset before age 45. Do not use for peripheral SpA (use ASAS 2011 peripheral criteria instead), modified New York criteria for AS only, or any case requiring actual radiology reading or laboratory HLA-B27 assay, which must be supplied by the caller.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-15T07:13:44.980Z","isFirstParty":false}