Table 4.
Sensitivity and specificity of the main entry criteria and other SpA-specific items for AS and axial SpA in primary care
| Criteria | Sensitivity for axial SpA (AS) % | Specificity for axial SpA (AS) % | Positive likelihood ratio | Negative likelihood ratio |
|---|---|---|---|---|
| Morning stiffness >30 min | 35.4 (46.8) | 66.5 (68.0) | 1.1 | 1.0 |
| Improvement by movement not by rest | 77.9 (83.0) | 39.7 (36.4) | 1.3 | 0.6 |
| Waking up in the second half of the night because of back pain | 58.4 (70.2) | 57.5 (59.8) | 1.7 | 0.7 |
| Improvement by NSAIDs within 48 h | 93.8 (78.7) | 48.0 (48.3) | 1.8 | 0.1 |
| Alternating buttock pain | 24.8 (34.0) | 88.5 (88.5) | 2.2 | 0.9 |
| History of enthesitis | 15.0 | 91.9 | 1.9 | 0.9 |
| History of arthritis | 10.6 | 95.7 | 2.5 | 0.9 |
| Age <35 years | 77.0 | 43.5 | 1.4 | 0.5 |
| HLA B27 (as determined in primary care) | 35.4 | 90.9 | 3.9 | 0.7 |
| ≥3 criteria | 85.1 | 49.8 | 1.7 | 0.3 |
AS, ankylosing spondylitis; NSAID, non-steroidal anti-inflammatory drug; SpA, spondyloarthritis.