Results from the non-conclusive primary and their respective follow-up samples mostly from category #3 and #4 in Table 1.

a Results obtained from the primary samples using the three reference assays, and both the TRF immunoassays (with 10 min and 1 h incubation times), as indicated. All the primary samples are from category #3 and #4, as listed in Table 1. ‘Enzg.’ indicates Enzygnost syphilis EIA. ‘+’, ‘−’ and ‘+/−’ indicate positive, negative and indeterminate results, respectively, as obtained with the mentioned assays.
b Results obtained from the thirteen follow-up samples of their respective primary samples using Enzygnost syphilis, TPHA, VDRL and I-L (Inno-Lia Syphilis score line immunoassay) as reference assays, and both the TRF immunoassays (with 10 min and 1 h incubation times), as indicated. Ten out of 13 samples are from category #3 and #4, as listed in Table 1. Each primary sample had either one or none follow-up sample. ‘NA’ indicates that a follow-up sample was not available to us.
sample belongs to category #2 as divided in Table 1.
Sample not tested with TRF immunoassays in this study.
*The antibody titer obtained in TPHA assay is shown in parentheses. ‘ND’, indicates that the test was not done.
c Syphilis status indicates whether the person has, or has had syphilis previously, and is based upon the results of previous or follow-up samples and on the available clinical data. ‘N’ indicates a negative and ‘P’ indicates a positive status for syphilis. ‘?’ indicates that true syphilis status is unknown.
sample from a new-born baby, with borderline level of maternal antibodies (data not shown).