CXCL12 as a biological marker for the diagnosis of tuberculous pleurisy

Although a chemokine CXCL12 is implicated in some infectious diseases, especially those in which T cell-mediated immunity plays critical roles, the relevance of CXCL12 to tuberculosis has never been elucidated. To determine the clinical efficacy of CXCL12 as a diagnostic marker for tuberculous (TB) pleurisy, we measured CXCL12 concentration in pleural fluid and serum from patients with various etiologies. Of 60 patients with pleural fluid, the median age of TB patients was 52 which was significantly lower than 71 of non-TB patients (P 0.01). CXCL12 level in TB effusion (4456 ± 1013 pg/mL, n = 15) was significantly higher than non-TB effusion (2851 ± 1229 pg/mL, n = 45) (P 0.01). On the other hand, serum CXCL12 level showed no significant differences among TB pleurisy, non-TB pleurisy, and normal healthy subjects. The sensitivity and specificity of CXCL12 in pleural fluid for the diagnosis of TB pleurisy was 60.0% and 93.2% (cut-off value = 4600 pg/mL), respectively. Area under the receiver operating characteristic (ROC) curve (AUC) for CXCL12 was 0.84. As the source of CXCL12, pleural mesothelium, endothelium of pulmonary vessels, bronchial epithelium, multinucleated giant epithelioid cells, and macrophages were positive for CXCL12 staining. Increased CXCL12 level in pleural fluid could be an informative diagnostic marker for differentiating TB pleurisy from other etiologies.