Fig 1.
Flowchart depicting study procedures.
Fig 2.
Western blot analysis of human sera for urea dissociation test.
The positions of the four diagnostic T. pallidum antigens(Tp15 kDa, Tp17 kDa, Tp45 kDa and Tp47 kDa) were indicated on the left and right for different lot number of the Western blot test kit[S111220BD-09(lane2-15), S111220BD-10(lane1) and S111220BD-11(lane16-22)]. Lane 1–6: sera obtained from patients with false positive ELISA results, no bands of specific antigens of T. pallidum. Lane 7–14: sera obtained from patients with positive ELISA and CLIA results, more than one distinctive band of the specific antigens. Lane 15–22: sera obtained from patients with positive ELISA, ELISA-IgM and CLIA results, one distinctive band of the specific antigens at least.
Table 1.
The results of antibodies to T. pallidum of 297 serum samples detected by different methods.
Fig 3.
Urea dissociation test to determine appropriate dissociation concentration and time.
The curve showed continuous changes of dissociation results at 0mol/L, 2mol/L, 4mol/L, 6mol/L, 8mol/L and 10mol/L dissociation concentration with 5min, 10min and 20min dissociation time of urea for different group. A1~A3: for 6 false-positive samples. B1~B3: for 8 IgG-positive and IgM-negative samples as control group. C1~C3: for 8 IgG-positive and IgM-positive samples as another control group.
Fig 4.
Comparation the detected results of antibodies to T.pallidum between ELISA and improved ELISA.
The value of S/CO of antibodies to T.pallidum detected by improved ELISA were all reduced, compared to ELISA, but all greater than 1.00. The operation steps of ELISA were strictly followed by kit instruction, and improved ELISA was inserted one step as adding PBS contained 6mol/L for 10 minutes after the first washing step.