Statistically significant differences in faecal BAFF and calprotectin concentration were found between IBD and IBS (BAFF: P < 0.0001; calprotectin: P = 0.002), whereas no differences were observed in faecal BAFF and calprotectin content between IBS patients and healthy controls (BAFF: P = 0.976; calprotectin: P = 0.1004). The gene discussed is TNFSF13B; the disease is inflammatory bowel disease.