The One Step Anti-TP (Treponema Pallidum /Syphilis) Test uses a double antigens sandwich principle for the detection of Syphilis antibody in human serum. A recombinant syphilis antigen (TP Ag 2) was immobilized on the test band region, and an antibody to syphilis on the control band region of nitrocellulose membrane. Another syphilis antigen (TP Ag 1), coupled with colloidal gold particles, is dried on a conjugate pad. During the assay, the specimen is allowed to react with the colored conjugate (antigen-colloid gold conjugate); the mixture then migrates chromatographically along the membrane by capillary action. If the specimen contains syphilis antibody, the recombinant antigen immobilized on the membrane will capture the antibody-antigen-colloidal gold complex and form a colored test band on the membrane, indicating a positive result. Absence of the test band s ests a negative result. To serve as a procedural control, a colored band at control region always appears in the test area.