Reduced circulating CH50 activity 2017-04-23T16:53:06Z Reduced circulating 50% hemolytic complement (CH50) activity HP:0031906 Reduced CH50 Decreased total hemolytic complement activity Reduced hemolytic complement activity A diminished activity of the classical complement pathway as measured by the assay for 50% haemolytic complement (CH50) activity of serum. Individual complement components can be quantified however this does not provide any information as to the activity of the pathway. The CH50 is a screening assay for the activation of the classical complement pathway and it is sensitive to the reduction, absence and/or inactivity of any component of the pathway. The CH50 tests the functional capability of serum complement components of the classical pathway to lyse sheep red blood cells (SRBC) pre-coated with rabbit anti-sheep red blood cell antibody (haemolysin). When antibody-coated SRBC are incubated with test serum, the classical pathway of complement is activated and haemolysis results. If a complement component is absent, the CH50 level will be zero; if one or more components of the classical pathway are decreased, the CH50 will be decreased. Abnormal total hemolytic complement activity