3.5 CXCL13 as a potential differentiation marker of active SLE from inactive SLE and of high-avidity IgG ANAs from low-avidity IgG ANAs in SLE patients
To evaluate the diagnostic potential and discriminatory accuracy of the serum CXCL13 concentration for active SLE and high-avidity IgG ANAs in SLE, receiver operating characteristic (ROC) curve analysis and the corresponding AUC values were determined (Figure 4). ROC curve analysis revealed that the serum CXCL13 levels were robust in discriminating patients with active SLE from inactive SLE and from high-avidity IgG ANAs from low-avidity IgG ANAs in SLE patients, with AUC values of 0.832 (95% CI 0.741–0.922, p < 0.0001) and 0.762 (95% CI 0.667–0.856, p = 0.0001), respectively. The maximal Youden’s index indicated that 150.27 pg/mL and 187.16 pg/mL were the best cut-off values to distinguish between active SLE and inactive SLE and between high-avidity IgG ANAs and low-avidity IgG ANAs in SLE patients, where the sensitivity and specificity were 89 and 90%, 86.3 and 88%, respectively.