Table 2 Selected baseline findings and their relation to the diagnosis of RA at 2 years follow-up
Occurrence at baseline in patients fulfilling RA criteria 2 years later (%)Occurrence at baseline in patients not fulfilling RA criteria 2 years later (%)SensitivitySpecificityAccuracyPPVNPV
Rheumatoid factor (>17 IE/ml)36330.360.670.590.290.74
s-CRP (>10 mg/l)64400.640.630.630.390.83
Radiography: Larsen grade 13630.360.970.800.800.81
MRI synovitis compatible with RA100401.000.600.710.481.00
MRI erosions compatible with RA64230.640.770.730.500.85
Scintigraphy compatible with RA64260.640.740.710.500.83
MRI synovitis or MRI erosion (both compatible with RA)100501.000.500.630.421.00
MRI synovitis and MRI erosion (both compatible with RA)64130.640.870.800.640.87
MRI synovitis and MRI erosion and scintigraphy (all compatible with RA)4500.451.000.841.000.82
  • PPV, positive predictive value; NPV, negative predictive value; s-CRP, serum C-reactive protein; MRI, magnetic resonance imaging; RA, rheumatoid arthritis.

  • Values in columns 1–2 denote the frequency of findings at baseline. Values in the other columns denote the relation between the baseline finding and the diagnosis of RA at 2 years’ follow-up.

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

  • 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.