Assess patients with hereditary deficiency of this component or acquired decrease in its level which may be seen due to hypercatabolism in hereditary angioneurotic edema, or consumption or loss as in vasculitides, glomerulonephritides, immune complex diseases. C₂ deficiency is the most common complement deficiency (1 in 10,000) and is associated with SLE.

Results of this test are labeled for research purposes only by the assay's manufacturer. The performance characteristics of this assay have not been established by the manufacturer. The result should not be used for treatment or for diagnostic purposes without confirmation of the diagnosis by another medically established diagnostic product or procedure. The performance characteristics were determined by LabCorp.

Deficiencies of C₁ components, C₂ and C₄ are associated with rheumatic diseases, including lupus, vasculitis, and dermatomyositis. Some individuals with deficiency may have no evidence of disease. The most common complement deficiency is C₂, which is a homozygous abnormality in 1 in 10,000 to 40,000 individuals, and is heterozygous in 1% to 2% of the general population. Patients with C₂ deficiency and lupus often have negative or low titer ANA.