Table 1 Baseline characteristics of study patients
Sex (% female)85%
Median (range) age (years)55 (17–78)
Median (range) symptom duration (years)1.5 (0.5–15)
Median (range) tender joint count (0–40)6 (0–30)
Median (range) swollen joint count (0–40)4 (2–18)
Median (range) serum CRP (mg/l)10 (<8–102)
Median (range) ESR (mm/h)8 (1–54)
Median (range) IgM rheumatoid factor (IU/ml)10 (<8–102)
Conventional radiography (no of patients)
    Normal19
    Compatible with RA (Larsen grade 1)5
    Minimal OA changes13
    Calcinosis4
MRI synovitis (no of patients)
    Normal15
    Compatible with RA23
    Compatible with OA2
    Compatible with RA/OA0
    Only tenosynovitis1
MRI erosions (no of patients)
    Normal27
    Compatible with RA14
    Compatible with OA0
    Compatible with RA/OA0
Bone scintigraphy* (no of patients)
    Normal14
    Compatible with RA10
    Compatible with OA10
    Compatible with RA/OA4
  • RA, rheumatoid arthritis; OA, osteoarthritis.

  • Larsen grade 1 denotes the presence of joint space narrowing, soft tissue swelling and/or juxta-articular osteoporosis.

  • MRI synovitis patterns: compatible with RA: several joints, not 1st carpometacarpal (CMC1) joints; compatible with OA: CMC1; compatible with RA/OA: mixed involvement of CMC1 and other joints.

  • MRI erosion patterns: compatible with RA: other joints than CMC1; compatible with OA: CMC1; compatible with RA/OA: mixed involvement of CMC1 and other joints.

  • Scintigraphic patterns: compatible with RA: several joints but not distal interphalangeal (DIP) joints and CMC1; compatible with OA: CMC1 or proximal interphalangeal (PIP) and DIP joints; compatible with RA/OA: mixed involvement of CMC1/DIP joints and other joints, eg, MCP/wrist joints.

  • *In three patients bone scintigraphy was not performed.