Table 3.
Optimal BASDAI cut-off values corresponding to ASDAS cut-offs using ROC curve with Youden's J statistic in AS patients.
| BASDAI cut-off | AUC (95% CI) | Specificity (95% CI) | Specificity (95% CI) | PPV (95% CI) | NPV (95% CI) | |
|---|---|---|---|---|---|---|
| ASDAS-CRP 1.3 | 2.1 | 0.76 (0.72–0.80) | 0.70 (0.65–0.75) | 0.82 (0.75–0.88) | 0.92 (0.88–0.95) | 0.50 (0.43–0.57) |
| ASDAS-CRP 2.1 | 3.1 | 0.78 (0.74–0.82) | 0.69 (0.62–0.76) | 0.87 (0.83–0.91) | 0.76 (0.68–0.82) | 0.83 (0.79–0.87) |
| ASDAS-CRP 3.5 | 3.7 | 0.82 (0.75–0.89) | 0.84 (0.66–0.95) | 0.81 (0.77–0.84) | 0.23 (0.15–0.31) | 0.99 (0.97–1.00) |
| ASDAS-ESR 1.3 | 2.0 | 0.80 (0.77–0.84) | 0.74 (0.69–0.78) | 0.87 (0.80–0.92) | 0.94 (0.90–0.96) | 0.56 (0.48–0.62) |
| ASDAS-ESR 2.1 | 2.6 | 0.79 (0.76–0.83) | 0.81 (0.74–0.86) | 0.78 (0.73–0.82) | 0.66 (0.59–0.73) | 0.88 (0.84–0.92) |
| ASDAS-ESR 3.5 | 4.8 | 0.79 (0.70–0.89) | 0.67 (0.46–0.83) | 0.92 (0.89–0.94) | 0.33 (0.21–0.47) | 0.98 (0.96–0.99) |
ASADS, ankylosing spondylitis disease activity score; AS, ankylosing spondylitis; AUC, area under the curve; BASDAI, bath ankylosing spondylitis disease activity index; CI, confidence interval; CRP, C-reactive protein; ESR, erythrocyte sedimentation rate; ROC, receiver operating characteristic; PPV, positive predictive value; NPV, negative predictive value.