Total Leiden score = sum of weighted baseline variables. Age contributes 0.02 points per year. All other components are categorical.

Variable	Points
Age	0.02 × age in years
Female sex	+1
Small joints of hands or feet involved	+0.5
Symmetric joint involvement	+0.5
Upper extremities involved (beyond hands/feet)	+1
Both upper and lower extremities involved	+1.5
Morning stiffness VAS 26–90 mm	+1
Morning stiffness VAS >90 mm	+2
Tender joint count 4–10	+0.5
Tender joint count ≥11	+1
Swollen joint count 4–10	+0.5
Swollen joint count ≥11	+1
C-reactive protein 5–50 mg/L	+0.5
C-reactive protein >50 mg/L	+1.5
Rheumatoid factor positive	+1
Anti-CCP (ACPA) positive	+2

Approximate total score range is 0–14. Higher values indicate greater 1-year risk of developing rheumatoid arthritis.

Leiden Clinical Prediction Rule for Undifferentiated Arthritis