As can be seen in Figure 1, conventional methodology such as the erythrocyte aggregation assay based on the Diamed-ID Micro Typing System was unable to detect defective antibody production in the majority of CVID patients, as a considerable proportion (approximately 2/3) of these patients can produce normal levels of anti-A/B IgM antibodies. This evidence concerns the gene CD40LG and common variable immunodeficiency.