Baseline level of functional C1-inhibitor correlates with disease severity scores in hereditary angioedema

The diagnosis of hereditary angioedema (HAE) is based on complement tests. We studied for the first time the possible association between complement parameters measured at the time of diagnosis and disease severity in 115 patients with HAE.Serum levels of functional C1-inhibitor (C1-INHf), antigenic C1-inhibitor (C1-INHa), C4 and hemolytic activity of the classical pathway (CH50) were determined at the time of diagnosis. We found a significant correlation between severity scores and baseline C1-INHf levels, as determined by ELISA assay (p = 0.0003). On the other hand, there was no correlation between severity scores and other complement parameters (C1-INHa, C4, and CH50).We consider the correlation between severity scores and baseline C1-INHf levels an important pathophysiological observation. Our findings underlie the potential significance of monitoring functional C1-INH levels in relation to clinical disease course.