{"uid":"cap_I-jNHjnKYEf6nlqttEhgK","slug":"leiden-arthritis-prediction-rule-calculator-van-der-helm-van-mil-2007-a656f6c8","name":"Leiden Arthritis Prediction Rule Calculator (van der Helm-van Mil 2007)","description":"van der Helm-van Mil 2007 Leiden prediction rule for recent-onset undifferentiated arthritis (Figure 1 / Table 2). Age × 0.02, female 1, small joints 0.5, symmetric 0.5, upper 1 or upper-and-lower 1.5, 100-mm morning-stiffness VAS 0/1/2, tender and swollen counts 0/0.5/1, CRP mg/L 0/0.5/1.5, RF 1, anti-CCP 2. Round to nearest 0.0 or 0.5. Bands ≤6 low, >6 and <8 indeterminate, ≥8 high. Not a diagnosis of RA. magent does not examine joints or assay serologies.","url":"https://api.magentlab.com/api/calc/leiden_arthritis","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":["age","sex","small_joints_hands_feet","symmetric","upper_extremities","upper_and_lower_extremities","morning_stiffness_vas_mm","tender_joint_count","swollen_joint_count","crp_mg_l","rheumatoid_factor_positive","anti_ccp_positive"],"properties":{"age":{"type":"integer","description":"Age in years as an integer from 18 to 120 (van der Helm-van Mil 2007). Scores age_years × 0.02. magent does not assign age."},"sex":{"enum":["female","male"],"type":"string","description":"Caller-assigned sex (van der Helm-van Mil 2007). female scores 1; male scores 0. magent does not assign sex."},"crp_mg_l":{"type":"number","description":"Caller-assigned C-reactive protein in mg/L (van der Helm-van Mil 2007). Number 0–500. 0–4 scores 0; 5–50 scores 0.5; ≥51 scores 1.5. magent does not assay CRP."},"symmetric":{"type":"boolean","description":"Symmetric joint involvement (van der Helm-van Mil 2007). true scores 0.5 and may stack with small-joint and extremity rows. magent does not examine joints."},"anti_ccp_positive":{"type":"boolean","description":"Caller-assigned anti-CCP (ACPA) positivity (van der Helm-van Mil 2007). true scores 2. magent does not assay serologies."},"upper_extremities":{"type":"boolean","description":"Involvement of upper extremities only (van der Helm-van Mil 2007). true scores 1 unless upper_and_lower_extremities is true, in which case this row is ignored. Mutually exclusive with the 1.5 upper-and-lower row. magent does not examine joints."},"tender_joint_count":{"type":"integer","description":"Caller-assigned tender joint count (van der Helm-van Mil 2007). Integer 0–68. <4 scores 0; 4–10 scores 0.5; ≥11 scores 1. magent does not examine joints."},"swollen_joint_count":{"type":"integer","description":"Caller-assigned swollen joint count (van der Helm-van Mil 2007). Integer 0–66. <4 scores 0; 4–10 scores 0.5; ≥11 scores 1. magent does not examine joints."},"small_joints_hands_feet":{"type":"boolean","description":"Involvement of small joints of the hands or feet (van der Helm-van Mil 2007). true scores 0.5 and may stack with symmetric and the extremity row. magent does not examine joints."},"morning_stiffness_vas_mm":{"type":"number","description":"Morning-stiffness severity on a 100-mm VAS (van der Helm-van Mil 2007), not duration in minutes. Number 0–100. 0–25 scores 0; 26–90 scores 1; >90 scores 2. magent does not take a history."},"rheumatoid_factor_positive":{"type":"boolean","description":"Caller-assigned rheumatoid factor positivity (van der Helm-van Mil 2007). true scores 1. magent does not assay serologies."},"upper_and_lower_extremities":{"type":"boolean","description":"Involvement of upper and lower extremities (van der Helm-van Mil 2007). true scores 1.5 and ignores upper_extremities. magent does not examine joints."}}}},"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_pvLuN2SJqq1JutCP1r98V","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":"Computes the van der Helm-van Mil 2007 Leiden prediction rule score for recent-onset undifferentiated arthritis to stratify risk of RA development into low, indeterminate, or high bands.","exampleAgentPrompt":"Apply the van der Helm-van Mil 2007 Leiden prediction rule for this patient: 52-year-old female, small joints of hands and feet involved, symmetric, upper extremities only, morning stiffness VAS 70 mm, 5 tender joints, 3 swollen joints, CRP 18 mg/L, rheumatoid factor positive, anti-CCP negative — what's her RA risk band?","exampleUseCases":[{"title":"Triage undifferentiated arthritis clinic referral","prompt":"I have a 45-year-old male patient with recent-onset arthritis — small joints not primarily involved, not symmetric, upper extremities only, morning stiffness VAS 30 mm, 2 tender joints, 1 swollen joint, CRP 3 mg/L, RF negative, anti-CCP negative. Can you run the Leiden 2007 prediction rule and tell me if he's low, indeterminate, or high risk for RA?"},{"title":"Serology-positive early arthritis scoring","prompt":"Score this early arthritis patient on the Leiden van der Helm-van Mil rule: she's 61, female, small joints of hands and feet involved, symmetric arthritis, both upper and lower extremities, morning stiffness VAS 85 mm, 8 tender joints, 6 swollen joints, CRP 55 mg/L, RF positive, anti-CCP positive."},{"title":"Low-risk ruling out RA progression","prompt":"Use the Leiden 2007 arthritis prediction rule for a 38-year-old male with no small joint involvement, non-symmetric, upper extremities only, VAS morning stiffness 10 mm, 1 tender joint, 0 swollen joints, CRP 2 mg/L, RF negative, anti-CCP negative — is he low risk for developing RA?"}],"resultDescription":"Returns the computed Leiden prediction rule total score (rounded to nearest 0.0 or 0.5) and a risk band classification: ≤6 = low, >6 and <8 = indeterminate, ≥8 = high. This is a risk stratification tool, not a diagnosis of rheumatoid arthritis.","failureModes":["Missing required query parameter returns an error (all 12 parameters are required)","Out-of-range age (e.g. below 18 or above 120) may cause validation failure","Invalid enum value for sex (must be 'female' or 'male') causes rejection","Non-boolean values for boolean fields cause schema validation errors","CRP values outside 0–500 mg/L range may not be handled gracefully","Conflicting extremity flags (both upper_extremities and upper_and_lower_extremities true) may produce unexpected scores — upper_and_lower takes precedence"],"whenToPreferThis":"Use this endpoint when you need a fast, reproducible implementation of the van der Helm-van Mil 2007 Leiden prediction rule specifically for recent-onset undifferentiated arthritis risk stratification. Prefer it over general clinical calculators when the exact published scoring weights and band thresholds (≤6 low, >6–<8 indeterminate, ≥8 high) are required. Not appropriate for established RA diagnosis, pediatric patients, or other arthritis prediction rules.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-15T12:52:30.140Z","isFirstParty":false}