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The influence of host factors (tobacco use, dentition, bleeding gums, oral rinsing, nasal medications, and time since the last meal) on immunoglobulin G (IgG) concentration in oral fluids (OF) was determined by univariate and multivariate analysis. Significant differences in IgG concentration were found to be associated with human immunodeficiency virus (HIV) status (HIV antibody positive, +16.60 μg/ml, P = 0.0001), sex (female, +1.23 μg/ml, P = 0.004), dentition (+2.83 μg/ml, edentulous versus dentulous, P = 0.0001), bleeding gums (+6.35 μg/ml, P = 0.0001), and time since the last meal (+3.55 μg/ml, >6 h, P = 0.0001). These factors could impact diagnostic methods that rely on the immunoglobulin concentration in OF specimens.

A comparative study was made of the single radial immunodiffusion test and the classical quantitative precipitin test for determining the amount of precipitable antibodies present in streptococcal groups A and C antisera. The potency of 21 group A and 54 group C antisera was determined by both methods; purified group-specific carbohydrates were used as antigens. The coefficient of correlation between the results from the two methods was 0.976 for group A antisera and 0.946 for group C antisera. When the concentration of antigen, the volume of antiserum used, and the depth of the antigen-agar mixture are kept constant, the diameter of the precipitin disc is directly related to the concentration of precipitable antibodies present in the antiserum. The use of the radial immunodiffusion test for evaluating and standardizing streptococcal grouping antisera is discussed as well as the advantages and disadvantages of using a concentrated vaccine for producing these antisera.