Eight biomarkers could statistically discriminate samples from pSS versus SLE patients.Four could statistically discriminate pSS patients from RA patients.None of the studied biomarkers could simultaneously discriminate pSS from RA and SLE. We, therefore, determined the positive predictive value (PPV), sensitivity, and specificity of different combinations of BDNF, I-TAC/CXCL11, sCD163 and Fractalkine/CX3CL1 concentrations. These biomarkers were chosen because they were those most strongly associated with distinguishing pSS from the other AIDs. The gene discussed is BDNF; the disease is AIDS.