CH50 assay

a functional assay of total complement activity that measures the capacity of serial dilutions of serum to lyse a standard preparation of sheep red blood cells coated with antisheep erythrocyte antibody. The reciprocal of the dilution of serum that lyses 50 per cent of the erythrocytes is reported as the whole complement titer in CH50 units per milliliter of serum. Called also hemolytic, total, or whole complement a.