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Leiden Arthritis Prediction Rule Calculator (van der Helm-van Mil 2007)
x402
Leiden Arthritis Prediction Rule Calculator (van der Helm-van Mil 2007) is a paid API for AI agents from api.magentlab.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-13).
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.
Price / call$0.005
Success—
StatusUnknown
How this service works
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.
Output
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.
Example use cases
Triage undifferentiated arthritis clinic referral
“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?”
Serology-positive early arthritis scoring
“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.”
Low-risk ruling out RA progression
“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?”
Technical details
Endpoint
GEThttps://api.magentlab.com/api/calc/leiden_arthritisWhen to prefer
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.
Side effects
- 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
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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