Sensitivity analysis
| Pretest Prob. (%) | SpA features | Post-test prob. (%) | ||
|---|---|---|---|---|
| The disease prevalence (pretest probability) and enthesitis were chosen as examples to illustrate effects of variation of these parameters on the post-test probability. A range of 1–10% for the disease prevalence and the consecutive post-test probabilities are given using constant test features (presence of IBP, HLA-B27, and uveitis). Likewise, we chose different LRs (resulting from different sensitivities and specificities) of the test parameter “enthesitis” using either a disease prevalence of 5% (assumed to be representative throughout the study) or also other possible prevalences of 3% and 7%, respectively. | ||||
| *Figures in bold indicate figures that are varied in this sensitivity analysis (either for disease prevalence or for sensitivity and specificity of enthesitis). The resulting post-test probabilities are also shown in bold; †figures assumed to be representative for either prevalence or SpA features which were taken for the calculations throughout the study; ‡the LR of 2.5 results from a sensitivity of 25% and a specificity of 90% (see table 1; Boyer et al27); §the LR of 7.8 results from a sensitivity of 47% and a specificity of 94% (see table 1; Collantes-Estevez et al28). | ||||
| 1* | IBP (LR 3.1)† | HLA-B27 (LR 9.0)‡† | Uveitis (LR 7.3)† | 67 |
| 2 | IBP (LR 3.1) | HLA-B27 (LR 9.0) | Uveitis (LR 7.3) | 80 |
| 3 | IBP (LR 3.1) | HLA-B27 (LR 9.0) | Uveitis (LR 7.3) | 86 |
| 4 | IBP (LR 3.1) | HLA-B27 (LR 9.0) | Uveitis (LR 7.3) | 89 |
| 5† | IBP (LR 3.1) | HLA-B27 (LR 9.0) | Uveitis (LR 7.3) | 91 |
| 7 | IBP (LR 3.1) | HLA-B27 (LR 9.0) | Uveitis (LR 7.3) | 94 |
| 10 | IBP (LR 3.1) | HLA-B27 (LR 9.0) | Uveitis (LR 7.3) | 96 |
| 5† | IBP (LR 3.1) | HLA-B27 (LR 9.0) | Enthesitis (LR 3.4)† | 83 |
| 5 | IBP (LR 3.1) | HLA-B27 (LR 9.0) | Enthesitis (LR 2.5)‡ | 78 |
| 5 | IBP (LR 3.1) | HLA-B27 (LR 9.0) | Enthesitis (LR 7.8)§ | 91 |
| 3 | IBP (LR 3.1) | HLA-B27 (LR 9.0) | Enthesitis (LR 2.5)‡ | 68 |
| 7 | IBP (LR 3.1) | HLA-B27 (LR 9.0) | Enthesitis (LR 7.8)§ | 94 |