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Quantitative liposome lysis by spectrophotometry
CH50 can be used to assess the integrity of the classical pathway (ie, the presence of complement components C1-C9), but cannot be used as a sensitive test for in vivo fixation of complement. A normal CH50 level indicates that all the components of the C1 through C9 are present; however, even in the presence of a normal CH50, the absolute levels of some complement components (eg, C3 or C4) can be significantly (50% to 80%) lower than normal without affecting CH50 activity. This is because normal serum contains C3 and C4 in substantial excess of that required to yield a normal result for CH50. Depletion of alternative factors is not detected. For this reason, it may be necessary to measure individual complement components.
Specimen not transported frozen; gross lipemia; plasma specimen (Ascorbic acid, bilirubin, and hemoglobin do not have a significant effect on the measurement.)