For discriminating IBS overall from organic diseases, serum albumin (4 studies, 282 IBS and 312 organic, SMD = 2.15, 95% CI = 0.20, 4.11, p = 0.031) and faecal calprotectin (16 studies, 1591 IBS and 1685 organic, SMD = -1.13, 95% CI = -1.51, -0.75, p < 0.0001) were significantly different. Here, ALB is linked to irritable bowel syndrome.