Diagnostic Biomarkers for Uveitis: Serum BAFF and CXCL9 in Differentiating Ocular Sarcoidosis, Tuberculosis and Other Entities with Implication for QuantiFERON-Positive Uveitis.

Purpose: To evaluate serum B cell activating factor (BAFF) and CXCL9 as diagnostic biomarkers for ocular sarcoidosis and ocular tuberculosis (TB). We also explore their role in the stratification of patients with QuantiFERON (QFT)-positive uveitis without another identifiable cause.

Methods: Eighty uveitis patients with various entities were included: 10 with ocular sarcoidosis, 35 with TB-related uveitis (including 11 confirmed (ocular TB) and 24 QFT-positive uveitis of unknown cause) and 35 with other uveitis entities. Levels of serum BAFF and CXCL9 were measured.

Results: Serum BAFF was higher in ocular sarcoidosis compared to other groups (area under the curve (AUC) = 0.74; 95% CI: 0.53-0.96, p = 0.017). At an optimal serum BAFF cut-off point of 772.3 pg/ml, the sensitivity was 70.0% (95% CI: 39.7-89.2) and the specificity was 89.1% (95% CI: 77.0-95.3). Serum CXCL9 was comparable between ocular sarcoidosis and confirmed ocular TB but was significantly higher in these groups compared to other uveitis entities (AUC = 0.71, 95% CI: 0.57-0.86, p = 0.011). To differentiate ocular sarcoidosis and TB from other uveitis entities, CXCL9 (cutoff: 105.5 pg/ml) showed a sensitivity of 88.9% (95% CI: 67.2-98.0) and a specificity of 54.3% (95% CI: 38.2-69.5). High CXCL9 TB-related uveitis patients demonstrated a higher proportion of uveitis resolution when fully treated with antitubercular treatment (ATT) (p = 0.027).

Conclusions: Serum BAFF and CXCL9 serve as potential diagnostic biomarkers for differentiating ocular sarcoidosis, ocular TB and other uveitis entities. These might identify QFT-positive uveitis who are most in need of ATT.