**Note: All laboratory testing requires an authorizing physician. DHA Laboratory offers a Patient Direct Program that partners you with an authorizing physician. If you have any additional questions regarding the availability of testing, please contact our laboratory by telephone or email.**
Quantitation of C4 is used to detect individuals with inborn deficiency of this factor or those with immunologic disease in whom hypercatabolism of complement causes reduced levels. These diseases include lupus erythematosus, serum sickness, certain glomerulonephritides, chronic active hepatitis, and others.