The diagnosis of the most studied AE subtype, the HAE-C1-INH, can be established most precisely in case the following tests are performed: C1-INH function measurement, the antigenic level of the C1-INH protein, C4 and C1q concentration, as well as titers of anti-C1-INH antibodies (Table 1) (24). This evidence concerns the gene SERPING1 and hereditary angioedema.