Table 4 Sensitivity and specificity of original and refined sets of candidate classification criteria for axial SpA in 40% of randomly selected cases (test set) and in the 60% remaining cases (validation set)
Criteria for SpATest set (40% of cases)Validation set (60% of cases)
Sensitivity (%)Specificity (%)Sensitivity (%)Specificity (%)
Candidate criteria (original) set 1 (IBP experts*)87.773.687.774.3
Candidate criteria (original) set 2 (IBP experts* obligatory plus ⩾2 other SpA features)85.975.885.577.2
Candidate criteria (refined) set 3a (HLA-B27 obligatory plus ⩾2 other SpA features)81.783.383.384.9
Candidate criteria (refined) set 3b (HLA-B27 obligatory plus ⩾1 other SpA feature)83.777.885.974.7
Candidate criteria (refined) set 4 (HLA-B27 or unilateral radiographic sacroiliitis grade 2 obligatory plus ⩾2 other SpA features)83.083.384.684.9
Modified ESSG (with MRI)†87.769.283.362.9
Modified Amor (with MRI)‡83.375.882.678.4
  • *Inflammatory back pain (IBP) according to experts; at least four of five parameters present.14 †The European Spondylarthropathy Study Group (ESSG) criteria were modified in that active sacroiliitis on magnetic resonance imaging (MRI) was added to the list of parameters required in addition to IBP or synovitis. ‡The Amor criteria were modified in that active sacroiliitis on MRI was assigned 3 scoring points, similar to definite radiographic sacroiliitis. SpA, spondyloarthritis.