Fractional Dilution Procedure for Precise Titration of Hemagglutinating Viruses and Hemagglutination-Inhibiting Antibodies

Summary A precise but relatively simple procedure for carrying out hemagglutination and hemagglutination-inhibition titrations with 5 viruses is described. In brief, the procedure is based on the use of a series of fractional dilutions of material under test in steps of 0.1 log unit. The method does not require any special equipment and yields titration endpoints which are closely reproducible. An analysis of the precision of the procedure relative to replicate titrations and the reproduction of absolute titers is presented. Both in hemagglutination and in hemagglutination-inhibition titrations, the precision of the results obtained with this technique is comparable to that yielded by photometric procedures.