Serum carbohydrate antigen 153 as a predictor of interstitial lung disease associated with rheumatoid arthritis is positively correlated with serum Krebs von den Lungen-6

Table 4 AUC, optimal cut-off value, sensitivity, specificity, Youden’s index and p-value of CA153 for different severity of RA-ILD using a ROC curve

Variate	RA-no ILD vs. RA-ILD (RA-mild ILD + RA-advanced ILD)	RA-no ILD vs. RA-advanced ILD
CA153
AUC (95% CI)	0.66(0.59–0.74)	0.95(0.91–0.98)
Cut-off value, U/ml	9.00	11.45
Sensitivity	57.27%	95.65%
Specificity	72.03%	83.05%
Youden’s index	0.2930	0.7870
p-value	< 0.001	< 0.001

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