Use

This test is useful for the assessment of an undetectable total complement level, diagnosing congenital C1 deficiency, and diagnosing acquired deficiency of C1 inhibitor. The first component of the complement (C1) is composed of 3 subunits designated as C1q, C1r, and C1s. C1q binds to immunoglobulin complexed to antigen and initiates the complement cascade. Congenital deficiencies of early complement components result in an inability to clear immune complexes, often leading to increased incidence of immune complex diseases.