[5] The test is based on the capacity of an individual's serum to lyse sheep erythrocytes coated with anti-sheep antibodies (preferably rabbit IgG).
The individual's serum is diluted until a minimum concentration of 50% of the sheep's red blood cells are lysed.
If an individual has deficient or malfunctioning complement factors, then at a baseline they have decreased capacity to lyse the erythrocytes.
It can also be seen in systemic lupus erythematosus as a result of increased usage of complement factors due to the pathology of the autoimmune condition.
[7] Increased CH50 values means that their complement is hyperfunctional relative to normal, and this may be seen in cancer or ulcerative colitis[citation needed].