Table 1

 Representative values of sensitivity and specificity for several tests relevant for axial spondyloarthritis as evaluated previously,1,3 along with the resulting LR+ and LR−*

ParameterSensitivity (%)Specificity (%)LR+LR−
CRP, C-reactive protein; ESR, erythrocyte sedimentation rate; HLA, human leucocyte antigen; IBD, inflammatory bowel disease; LR+, positive likelihood ratio; LR−, negative likelihood ratio; NSAID, non-steroidal anti-inflammatory drugs; SpA, spondyloarthritis.
*LR+ = sensitivity/(1 – specificity); LR− = (1 – sensitivity)/specificity.
†As enthesitis, dactylitis, uveitis, peripheral arthritis, psoriasis and IBD may not be present at disease onset but may develop later, it is recommended to ignore a negative test result of these tests in an early state of possible axial SpA. The LR− of parameters, which should be ignored, are shown in brackets.
‡The figures for sensitivity and specificity of HLA-B27 refer to a European Caucasian population. In European Caucasian patients with psoriasis or IBD, a sensitivity of 50%, a specificity of 90%, an LR+ of 5.0 and an LR− of 0.56 for HLA-B27 should be applied. In other ethnic populations, sensitivity and specificity of HLA-B27 may be different, resulting in different LR+ and LR− (also discussed by Rudwaleit et al1).
Inflammatory type of back pain5,675763.10.33
Heel pain (enthesitis)37893.4(0.71)†
Peripheral arthritis40904.0(0.67)†
Iritis or anterior uveitis22977.3(0.80)†
Positive family history for axial SpA, reactive arthritis, psoriasis, IBD or anterior uveitis32956.40.72
Good response to NSAIDs77855.10.27
Raised acute-phase reactants (CRP/ESR)50802.50.63
Sacroiliitis shown by magnetic resonance imaging90909.00.11