As discussed below, IgGSc are also recommended as second-line tests in patients with low IgA and should be monitored in IgGScD patients for progression to common variable immunodeficiency (CVID).20-25 Whether first or second line, the measurement of IgGSc is an important test that provides a more complete picture of the humoral immune system. This evidence concerns the gene CD79A and common variable immunodeficiency.