As the Wassermann test is considered, and should be, a quantitative reaction, the correct titration of the reagents, especially complement and amboceptor, is of the utmost importance.
Wassermann,1 in the original communication, and Noguchi,2 as well as other writers on the subject, recommend the titration of complement and amboceptor without the addition of the other factors. That is, these two factors are mixed in varying quantities with a suspension of corpuscles. On incubation the smallest amount of the factor which, with a fixed quantity of the other, is required to produce complete hemolysis, is considered as one unit. For the actual test twice the unit is used. This method of titration is open to objection. Noguchi has pointed out that within certain limits complement and amboceptor are interchangeable. Further, it is a recognized fact that on the addition of patients' serum (whether positive or negative)
THOMPSON L. THE TITRATION OF WASSERMANN REAGENTS. Arch Intern Med (Chic). 1914;XIII(6):904-908. doi:10.1001/archinte.1914.00070120066005