Bactericidal screening test for late complement component deficiencies or defects

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Abstract
Congenital complement deficiency was described in disseminated Neisseria infections. Its occurrences in humans with other kinds of infections were not described. In the past, CH50 [total hemolytic complement] determinations were used to detect these deficiencies, but this procedure is time consuming and cumbersome. A method of determining the presence of late component deficiencies or defects is described which is easy and inexpensive to perform. An agar pour plate with a serum-sensitive Escherichia coli strain is made, and 2.5-mm wells are put in the agar. Unknown fresh sera are used to fill the wells. An absence of a zone of bacterial growth inhibition around the well after incubation at 37.degree. C overnight indicates a late component defect or deficiency in the test serum. By applying this assay to 35 selected patients, 4 deficient patients were identified. One had a congenital C5 deficiency and 3 had C6 deficiencies. It is suggested that the assay be used as a screeing test to study the relationship between congenital complement deficiencies and various kinds of infections, especially those caused by organisms which are partially serum sensitive.