Furthermore, the combination of low concentrations of BDNF and Fractalkine/CX3CL1 was highly specific for pSS (specificity 96.2%; positive predictive value 80%) in comparison to RA and SLE, as was the combination of high I-TAC/CXCL11 and low sCD163 (specificity 98.1%; positive predictive value 75%). The gene discussed is BDNF; the disease is rheumatoid arthritis.