FIG. 3.

Representative distribution of quantitative VDRL (A) and FTA-ABS IgM (B) assay titers, as reported by the participants of the proficiency testing trial held in September 2003. Distribution of titers for the positive sample 51/2003 (median VDRL test reference titer, 4; median FTA-ABS IgM test reference titer, 80) clearly demonstrates that test results are dependent on the manufacturer of the assay (for characterization of samples, see Table 3). Distribution of results as obtained by tests from different manufacturers is indicated by different gray scales. AX, bioMerieux; BB, Biokit; BN, Becton-Dickinson; BR, Biorad; BW, Dade Behring; IS, Innogenetics; MA, Mast.