From time to time, there are patients and friends with syphilis test labs, wondering why my syphilis antigen reactin test and syphilis specific antibody test is a positive and a negative, indeed for non-medical people and even beginners are difficult to explain, today we do a brief description of these two tests. The syphilis test results on the lab sheets that patients often get in their hands usually have two contents, one is TPPA and the other is TRUST/RPR: a. TPPA is called syphilis spirochete particle agglutination test, which detects specific spirochete antibodies, including IgM and IgG antibodies, IgM antibodies can appear early after infection, IgG antibodies can be present for a long time or even for life, and remain positive even after cure. Therefore, a positive TPPA indicates that the patient is acutely and presently infected or has been previously infected, and cannot be used as a basis for determining syphilis activity. Second, TRUST/RPR is called toluidine red unheated serum test/plasma reactin ring card test, different units may take different testing reagents, but the detection is the human body against the syphilis spirochete destruction of human cells released lipid-like substances and syphilis spirochete’s own lipid-like protein stimulation produced by IgM and IgG antibodies, commonly known as ” Reactin”. It can be detected only after about 6 weeks of infection, so it has poor diagnostic ability for early syphilis, but its titer changes can be used to observe the efficacy of syphilis. In addition, because the appearance of reactive elements after infection with syphilis is later than that of specific spirochete antibodies, the test may be negative in late syphilis because the body does not produce targeted antibodies. Therefore, the TRUST method is not applicable to the diagnosis of stage I syphilis and stage III syphilis. Therefore, if there has been high-risk sexual behavior, a positive TRUST/RPR can diagnose syphilis early, but early TPPA may be negative. And at the stage of stage 3 syphilis, TPPA may remain positive while TRUST/RPR turns negative because the organism cannot produce enough reactin.