FIG 2.

Use of more-concentrated serum in the TNA results in positive tests from convalescent-phase samples, while control samples remain negative. Serum from samples V018, V020, and V021 was tested for neutralization of ACT activity using a higher concentration of serum. Serum samples from a pertussis-positive subject (V008 and others not shown) and pertussis-negative control subjects (N030, N038, and others not shown) were also tested. The 1:20 dilution of serum sample V020 is significantly different from 1:20 dilutions of serum from pertussis-negative control samples N030 and N038. The 1:20 dilution of sample V021 is not significantly different (NS) from 1:20 dilutions of N030 or N038. Shown are P values from multiple comparison testing using ANOVA with Tukey's post hoc test to determine statistical significance (P ≤ 0.05). Data represent the mean and SD of the results from each sample tested in triplicate.