Laboratory Investigation of Complement Disorders

The service offered by clinical immunology laboratories should include not only the monitoring of complement activation but also the detection of complement deficiency syndromes. The total haemolytic complement assay, the alternative pathway haemolytic assay and the C3–C9 assay are simple to perform and their results locate the missing component to the classical pathway, the alternative pathways or the terminal sequences. Identification of the missing component requires the use of functional and immunochemical assays of individual components. These permit the discrimination between absence of a component, or the presence of a functionally inactive variant.