Interestingly, 82% of the patients with CVID, having had repeated measurements of CXCL13, did not cross the CXCL13 cut-off limit of 184 pg/ml, corroborating the consistency of CXCL13 measurements and the ability to characterise a patient with CVID by a single measurement of a biomarker (Fig. 3). This evidence concerns the gene CXCL13 and common variable immunodeficiency.