SERPING1 and hereditary angioedema: Baseline functional activity was inversely correlated with HAE attack frequency (i.e., lower baseline C1-INH activity was predictive of an increased attack rate during treatment; R = 0.2; P = 0.01); however, no significant relationship was observed between postinjection C1-INH function and attack frequency (R = 0.09; P = 0.3) (49).